"What is the color of your walls?"
Translation:Jakiego koloru są twoje ściany?
You could easily turn it around to: „Twoje ściany są jakiego koloru?”, which would literally translate as "Your walls are of what colour?" – whenever you see "of" in English, genitive is probably the answer in Polish. ;-)
A bit longer explanation is that the walls here are the subject of the sentence, but their colour is unknown, so question word jakiego(masculine genitive singular, because „kolor”) replaces the actual colour name. Then you just slap the question mark at the end of the sentence and switch word order so that the walls end up at the end, to stress that it is the thing you ask about – that is the very typical question formation in Polish language:
- To auto jest szybkie.
- Jakie jest to auto?
- Dom Piotrka jest wysoki.
- Jaki jest dom Piotrka?
- Twoja siostra jest bardzo miła.
- Jaka jest twoja siostra?
And so on. That is why „jaki, jaka, jakie" are pretty important words to know – if you know how to build a positive sentence and you know which form of „jaki” to use, you can build a question asking about pretty much every feature of a noun(with exception of possession, these use „czyj” or „kogo”) in Polish, by merely replacing it with the proper question word and switching word order. ;-)
Thank you! I knew there would need to be genitive somewhere, but I was having trouble assigning it to the color instead of the walls. Translating this as "Your walls are of what color" as you said (and which seems like the more literal translation) instead of "What is the color of your walls" as in the exercise helps a lot.