I see. But I'm referring to the "Tipps and Notes":
"In English, you use “to be” to describe color (the shirt is red, the dog is brown, the computer is black, etc.). In Vietnamese, we do not use “to be” but the verb “to have” - có.
Formula for this: S + có + màu + color. (Example: Con chó có màu nâu (literally, The dog has color brown)). Do not use “to be” with color!"
The formula said is equivalent to S + is + color in English. In this sentence, [color] plays the role of adjective after "to be". Therefore, you cannot use "là" here.
But this sentence uses a structure that I think both languages don't usually use: The colors of + S + are + [colors]. In this sentence, [color] plays the role of a noun after "to be". Therefore, "to be" is "là" here.
The consensus seems to be that this is bad (or unnatural) Vietnamese and bad (or unnatural) English.... So much for language learning...
I don't know if the Vietnamese is good or bad, but most English speakers will say "the shirt is red and white" and this totally gets the meaning of the Vietnamese sentence. Demanding a literal, word for word translation from Vietnamese to English does not get good results.