"Máš raději zelenou nebo žlutou?"

Translation: Do you prefer green or yellow?

[Tielbert]

Is it a feminine adjective because of barva?

[endless_sleeper]

Yep.

[Janmunroe]

Why did they use the feminine "zelenou" and "zlotou". Are they just assuming that "barva" is what they're modifying?

[VladaFu]

Basically yes, the colours are used in feminine as if the word barva were there.

[AukeBooij]

How do you say "Do you like green or yellow?" In other words, if you're not asking for a choice, just yes/no.

[JanLyko]

"Do you like green or yellow?" is literally "Máš rád/ráda zelenou nebo žlutou?" Technically you can answer with yes/no, but many people consider such answer insufficient or even rude.

[ValaCZE]

If you want yes/no answer, you have to ask only one color. "Máš rád/a zelenou?" - for green color; Máš rád/a žlutou?" - for yellow color.

[pdusek]

I disagree. You can easily ask whether I like any of given two colors. On the other hand, normally you would ask the question different way (as answer "yes, I like green or yellow" is rather provocative - although it is mathematically correct).

[HappyCamperVan]

My answer (marked incorrect, but should maybe be acceptable): "Do you like green or yellow better?"
The corrected I was given answer sounds wrong to me in English: "Do you like green more or yellow?" with "more" and "or" underlined.

[BoneheadBass]

Although my initial response would have been "Do you prefer green or yellow," and not realizing that you'd already been there, I answered (experimentally) with "do you like green or yellow better" which, as you've pointed out, was not accepted. In case it's just a missing translation, I've reported it.

[nnfarias]

Why is it raději instead of rad or rada?

[Tielbert]

I guess, it's a comparative adjective: more rad