Do Buddhist texts record or comment on the then-prevalent varna or caste systems?

When people joined the Buddha's Sangha or monastic community, they lost their former worldly caste status, as follows:

Just as the mighty rivers on reaching the great ocean lose their former names and designations and are just reckoned as the great ocean; even so, when members of the four castes—nobles, brahmins, commoners and menials—go forth from home into the homeless life in this Dhamma and Discipline proclaimed by the Tathāgata, they lose their former names and lineage and are reckoned only as ascetics following the Son of the Sakyans. This is the fourth wonderful and marvellous quality in this Dhamma and Discipline…

The Simile of the Ocean.

However, the Buddha did not oppose the caste system in non-Buddhist society despite often emphasizing to Brahmins they are not noble or Brahmin by 'birth' ('family lineage') but noble due to their actions (kamma), as follows:

For name and clan are assigned as mere convention in the world. Arising by mutual agreement, they’re assigned to each individual.

For a long time this misconception has prejudiced those who don’t understand. Ignorant, they declare that one is a brahmin by birth.

You’re not a brahmin by birth, nor by birth a non-brahmin. You’re a brahmin by your deeds, and by deeds a non-brahmin.

You’re a farmer by your deeds, by deeds you’re a professional; you’re a trader by your deeds, by deeds are you an employee;

you’re a bandit by your deeds, by deeds you’re a soldier. you’re a sacrificer by your deeds, by deeds you’re a ruler.

In this way in accord with truth, the astute regard deeds. Seeing dependent origination, they’re expert in deeds and their results.

MN 98

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Vāseṭṭha, there are these four castes: aristocrats, brahmins, merchants, and workers. Some aristocrats kill living creatures, steal, and commit sexual misconduct. They use speech that’s false, divisive, harsh, and nonsensical. And they’re covetous, malicious, with wrong view. These things are unskillful, blameworthy, not to be cultivated, unworthy of the noble ones—and are reckoned as such. They are dark deeds with dark results, criticized by sensible people. Such things are seen in some aristocrats. And they are also seen among some brahmins, merchants, and workers.

But some aristocrats refrain from killing living creatures, stealing, and committing sexual misconduct. They refrain from speech that’s false, divisive, harsh, and nonsensical. And they’re content, kind-hearted, with right view. These things are skillful, blameless, to be cultivated, worthy of the noble ones—and are reckoned as such. They are bright deeds with bright results, praised by sensible people. Such things are seen in some aristocrats. And they are also seen among some brahmins, merchants, and workers.

DN 27

MN 95 states about the Buddha:

He doesn’t wish any harm upon the community of brahmins. …

DN 27 describes a 'brahmin' as follows:

Then some of those same beings thought: ‘Oh, how wicked things have appeared among beings, in that stealing is found, and blaming and lying and the taking up of rods and banishment! Why don’t we set aside bad, unskillful things?’ So that’s what they did. ‘They set aside bad, unskillful things’ is the meaning of ‘brahmin’, the first term to be specifically invented for them.

Straight forward answer is Buddhism never accept caste system or the color. In "Wasala suthra" (as I remember the name) Lord Buddha has clearly mentioned that, a person doesn't become noble by his birth, caste etc but by his act (behavior).

Vasala Sutta: Discourse on Outcasts (SN 1.7)

Now at that time a fire was burning, and an offering was being prepared in the house of the brahman Aggikabharadvaja. Then the Blessed One, while on his alms round, came to the brahman's residence. The brahman seeing the Blessed One some way off, said this: "Stay there, you shaveling, stay there you wretched monk, stay there you outcast." When he spoke thus the Blessed One said to the brahman: "Do you know, brahman, who an outcast is and what the conditions are that make an outcast?" "No, indeed, Venerable Gotama …

Regardless of the type of caste one is in, all have an equal opportunity to become enlightened.

From the Gihi Sutta:

In the same way,
wherever one is born
among human beings —
noble warriors, brahmans,
merchants, workers,
outcastes, or scavengers —
if one is tame,
with good practices,
righteous,
consummate in virtue,
a speaker of truth,
with conscience at heart,
one who's abandoned birth & death,
completed the holy life
put down the burden,
done the task
fermentation-free,
gone beyond all dhammas,
through lack of clinging
unbound:
offerings to this spotless field
bear an abundance of fruit.