Isaiah 1:18

יהיו

they are becoming

9016

None
Definition: verseEnd
Root: None
Exhaustive: None

|

1961

היה
hâyâh
Definition: to exist, i.e. be or become, come to pass (always emphatic, and not a mere copula or auxiliary)
Root: a primitive root (compare H1933 (הוא));
Exhaustive: a primitive root (compare הוא); to exist, i.e. be or become, come to pass (always emphatic, and not a mere copula or auxiliary); beacon, [idiom] altogether, be(-come), accomplished, committed, like), break, cause, come (to pass), do, faint, fall, [phrase] follow, happen, [idiom] have, last, pertain, quit (one-) self, require, [idiom] use.

כ צמר

as wool

6785

צמר
tsemer
Definition: wool
Root: from an unused root probably meaning to be shaggy;
Exhaustive: from an unused root probably meaning to be shaggy; wool; wool(-len).

|

9004

כ
None
Definition: like, as
Root: Derived terms כאשר‎ (ka'ashér) כמו‎ (k'mó) כמות‎ (k'mót) כש־‎ (k'she-)
Exhaustive: prefix, particle of comparison, similarity or proportion; before Sheva, with article - as, like, as if; at, about [a time], according to, after; before an infinitive - as, when, if, after.

כ תולע

as the worm

8438a

תולע
tôwlâʻ
Definition: the crimson-grub, but used only (in this connection) of the colorfrom it, and cloths dyed therewith
Root: and (feminine) תולעה; or תולעת; or תלעת; from H3216 (ילע); a maggot (as voracious); specifically (often with ellipsis of H8144 (שני))
Exhaustive: and (feminine) תולעה; or תולעת; or תלעת; from ילע; a maggot (as voracious); specifically (often with ellipsis of שני); the crimson-grub, but used only (in this connection) of the colorfrom it, and cloths dyed therewith; crimson, scarlet, worm.

|

9004

כ
None
Definition: like, as
Root: Derived terms כאשר‎ (ka'ashér) כמו‎ (k'mó) כמות‎ (k'mót) כש־‎ (k'she-)
Exhaustive: prefix, particle of comparison, similarity or proportion; before Sheva, with article - as, like, as if; at, about [a time], according to, after; before an infinitive - as, when, if, after.

יאדימו

they are becoming red

119

אדם
ʼâdam
Definition: flush or turn rosy
Root: to show blood (in the face), i.e.
Exhaustive: to show blood (in the face), i.e.; flush or turn rosy; be (dyed, made) red (ruddy).

אם

if

9014

־
None
Definition: link
Root: None
Exhaustive: None

|

518a

אם
ʼim
Definition: used very widely as demonstrative, lo!; interrogative, whether?; or conditional, if, although; also Oh that!, when; hence, as a negative, not
Root: a primitive particle;
Exhaustive: a primitive particle; used very widely as demonstrative, lo!; interrogative, whether?; or conditional, if, although; also Oh that!, when; hence, as a negative, not; (and, can-, doubtless, if, that) (not), [phrase] but, either, [phrase] except, [phrase] more(-over if, than), neither, nevertheless, nor, oh that, or, [phrase] save (only, -ing), seeing, since, sith, [phrase] surely (no more, none, not), though, [phrase] of a truth, [phrase] unless, [phrase] verily, when, whereas, whether, while, [phrase] yet.

ילבינו

they are being made white

3835a

לבן
lâban
Definition: to be (or become) white; to make bricks
Root: a primitive root; also as denominative from H3843 (לבנה)
Exhaustive: a primitive root; also as denominative from לבנה; to be (or become) white; to make bricks; make brick, be (made, make) white(-r).

כ שלג

as snow

7950

שלג
sheleg
Definition: snow (probably from its whiteness)
Root: from H7949 (שלג);
Exhaustive: from שלג; snow (probably from its whiteness); snow(-y).

|

9004

כ
None
Definition: like, as
Root: Derived terms כאשר‎ (ka'ashér) כמו‎ (k'mó) כמות‎ (k'mót) כש־‎ (k'she-)
Exhaustive: prefix, particle of comparison, similarity or proportion; before Sheva, with article - as, like, as if; at, about [a time], according to, after; before an infinitive - as, when, if, after.

כ שנים

as two

8144

שני
shânîy
Definition: crimson, properly, the insect or its color, also stuff dyed with it
Root: of uncertain derivation;
Exhaustive: of uncertain derivation; crimson, properly, the insect or its color, also stuff dyed with it; crimson, scarlet (thread).

|

9004

כ
None
Definition: like, as
Root: Derived terms כאשר‎ (ka'ashér) כמו‎ (k'mó) כמות‎ (k'mót) כש־‎ (k'she-)
Exhaustive: prefix, particle of comparison, similarity or proportion; before Sheva, with article - as, like, as if; at, about [a time], according to, after; before an infinitive - as, when, if, after.

חטאי כם

the misses of yourselves

9026

כם
None
Definition: your, personal posessive - noun suffix: 2nd person masculine plural
Root: None
Exhaustive: Personal posessive pronoun - suffix for nouns, adjectives and passive participles: 2nd person masculine plural

|

2399

חטא
chêṭᵉʼ
Definition: a crime or its penalty
Root: from H2398 (חטא);
Exhaustive: from חטא; a crime or its penalty; fault, [idiom] grievously, offence, (punishment of) sin.

יהיו

they are becoming

1961

היה
hâyâh
Definition: to exist, i.e. be or become, come to pass (always emphatic, and not a mere copula or auxiliary)
Root: a primitive root (compare H1933 (הוא));
Exhaustive: a primitive root (compare הוא); to exist, i.e. be or become, come to pass (always emphatic, and not a mere copula or auxiliary); beacon, [idiom] altogether, be(-come), accomplished, committed, like), break, cause, come (to pass), do, faint, fall, [phrase] follow, happen, [idiom] have, last, pertain, quit (one-) self, require, [idiom] use.

אם

if

9014

־
None
Definition: link
Root: None
Exhaustive: None

|

518a

אם
ʼim
Definition: used very widely as demonstrative, lo!; interrogative, whether?; or conditional, if, although; also Oh that!, when; hence, as a negative, not
Root: a primitive particle;
Exhaustive: a primitive particle; used very widely as demonstrative, lo!; interrogative, whether?; or conditional, if, although; also Oh that!, when; hence, as a negative, not; (and, can-, doubtless, if, that) (not), [phrase] but, either, [phrase] except, [phrase] more(-over if, than), neither, nevertheless, nor, oh that, or, [phrase] save (only, -ing), seeing, since, sith, [phrase] surely (no more, none, not), though, [phrase] of a truth, [phrase] unless, [phrase] verily, when, whereas, whether, while, [phrase] yet.

יהוה

He Is

3068

יהוה
Yᵉhôvâh
Definition: Jehovah, Jewish national name of God
Root: from H1961 (היה); (the) self-Existent or Eternal;
Exhaustive: from היה; (the) self-Existent or Eternal; Jehovah, Jewish national name of God; Jehovah, the Lord. Compare יה, יהוה.

יאמר

he is saying

559

אמר
ʼâmar
Definition: to say (used with great latitude)
Root: a primitive root;
Exhaustive: a primitive root; to say (used with great latitude); answer, appoint, avouch, bid, boast self, call, certify, challenge, charge, [phrase] (at the, give) command(-ment), commune, consider, declare, demand, [idiom] desire, determine, [idiom] expressly, [idiom] indeed, [idiom] intend, name, [idiom] plainly, promise, publish, report, require, say, speak (against, of), [idiom] still, [idiom] suppose, talk, tell, term, [idiom] that is, [idiom] think, use (speech), utter, [idiom] verily, [idiom] yet.

ו נוכחה

and she has been corrected

3198

יכח
yâkach
Definition: to be right (i.e. correct); reciprocal, to argue; causatively, to decide, justify or convict
Root: a primitive root;
Exhaustive: a primitive root; to be right (i.e. correct); reciprocal, to argue; causatively, to decide, justify or convict; appoint, argue, chasten, convince, correct(-ion), daysman, dispute, judge, maintain, plead, reason (together), rebuke, reprove(-r), surely, in any wise.

|

9002

ו
None
Definition: and
Root: None
Exhaustive: Conjunctive vav - i.e. followed by prefix, suffix or non-verb (conjunctive) (‘and/but’)

נא

pray/please

4994

נא
nâʼ
Definition: 'I pray', 'now', or 'then'; added mostly to verbs (in the Imperative or Future), or to interjections, occasionally to an adverb or conjunction
Root: a primitive particle of incitement and entreaty, which may usually be rendered;
Exhaustive: a primitive particle of incitement and entreaty, which may usually be rendered; 'I pray', 'now', or 'then'; added mostly to verbs (in the Imperative or Future), or to interjections, occasionally to an adverb or conjunction; I beseech (pray) thee (you), go to, now, oh.

לכו

walk!

9014

־
None
Definition: link
Root: None
Exhaustive: None

|

1980

הלך
hâlak
Definition: to walk (in a great variety of applications, literally and figuratively)
Root: akin to H3212 (ילך); a primitive root;
Exhaustive: akin to ילך; a primitive root; to walk (in a great variety of applications, literally and figuratively); (all) along, apace, behave (self), come, (on) continually, be conversant, depart, [phrase] be eased, enter, exercise (self), [phrase] follow, forth, forward, get, go (about, abroad, along, away, forward, on, out, up and down), [phrase] greater, grow, be wont to haunt, lead, march, [idiom] more and more, move (self), needs, on, pass (away), be at the point, quite, run (along), [phrase] send, speedily, spread, still, surely, [phrase] tale-bearer, [phrase] travel(-ler), walk (abroad, on, to and fro, up and down, to places), wander, wax, (way-) faring man, [idiom] be weak, whirl.

RBT Translation:

walk please and she has been corrected he is saying He Is if they are becoming the misses of yourselves as two as snow they are being made white if they are becoming red as the worm as wool they are becoming

RBT Paraphrase:

She has been corrected

Walk, please! And she has been corrected,³ He Is is saying, if the misses of yourselves are as two, they are being made white as snow. If they are becoming red as the worm, they are becoming as wool.

Julia Smith Literal 1876 Translation:
Come now we will confute together Jehovah will say: if your sins shall be as deep scarlet, they shall be white as snow; if they shall be red as crimson, they shall be as wool.

LITV Translation:
Come now and let us reason together, says Jehovah: Though your sins are as scarlet, they shall be white as snow; though they are red as the crimson, they shall be like wool.

Brenton Septuagint Translation:
And come, let us reason together, saith the Lord: and though your sins be as purple, I will make them white as snow; and though they be as scarlet, I will make them white as wool.

Footnotes

Isa. 1:18

Hebrew ונוכחה and she has been corrected. She has been corrected, reasoned with, reproved, convicted, made right.

• נוכחה (nochacha) is the third person feminine singular in the Niphal, complete form.

The translation "let us reason together" is simply wrong. In fact, it is far from what the first person plural would look like which makes this a rather mischievious translation, at best.

The proper spelling for the first person plural form in the complete tense would be "נוכחנו" (nochachnu). This form is used when "we" are the subject of the sentence.