Would be wrong.
By the way, it would be a question in wich you usually had two options, you would have to pick one.
For example, if I am or another person is seeing two skirts, one green and one blue, chances are that I or the person asks you "which skirt is blue?"
If there were more alternatives, say, several skirts in several colours (and one blue among them), you problably would be asked the question "what
skirt is blue?" -not "what is blue skirt?'' - agreed?http://www.inglesnapontadalingua.com.br ... which.html
Notice that you (and others that are learning English) problably is used to the pattern of questions with "what + is", so you don´t feel anything weird about it. If you think of "which" as a cousin of "what" it can work as a mnemonics to memorize the pattern (I mean, a way to accept and remember how to use it on a regular basis).
I hope it helps.