"Is it light?"
This is only confusing. While it is true that "világos" can mean "it is light", the main use of the question "világos?" is in the meaning "is it clear"?
I didn't know what to make of this either because "is it light?" means "világos van?", meaning the sun is still up but "világos?" means "is it bright?" or as you said "is it clear?" figuratively.
I actually took "light" as a noun and wrote "az fény?". Needless to say, it was not accepted. But to me it seems the most reasonable interpretation :).
I took light as the opposite to heavy! OK, we are in a section on colours, but "light" without the colour being named just didn't register with this meaning.
I also thought like you. And I did not chose the colors lesson for strenthening, I just took the Strengthening button on the main page. So the sentences have to be accepted in any context.