Translation:The red bathroom does not have any windows.
That's not how it works. "Das rotes Bad" is wrong.
definite article -> weak inflection
I get what you mean, but two statements can be used to describe this situation:
"The bathroom has no windows."
"The bathroom doesn't have a window."
Both sentences say the same thing but they are conveyed using different words. The sentence that DuoLingo has us translate is the former (rather than the latter).