Translation:The red bathroom does not have any windows.
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).
That's not how it works. "Das rotes Bad" is wrong.
definite article -> weak inflection