The colour of the shirt is red and white is definitely a good variation in English
If you use 'có', it should be: Cái áo có màu đỏ và trắng. - "The shirt has red and white colors.", or more naturally "The shirt is red and white."
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.
I see. But maybe that should be in the notes. Then in the lessons suddenly "là" is used without there being an explanation about that...
The consensus seems to be that this is bad (or unnatural) Vietnamese and bad (or unnatural) English.... So much for language learning...