"Do you like red?"
It works as masculine inanimate adjective. Masculine inanimates' accusative is same as nominative.
It could be only "czerwonego" if speaking about a red-painted human, or someone who is a communist (that may be then referred to as "czerwony", which is somewhat derogatory name).
Not really. While I can't right now recall an animal that I would describe as "czerwony", I think there are some things that are "animated" and "red" in Polish language. (but squirrel's fur and human hair is not "czerwony" it's "rudy").
EDIT: some flowers are masculine, and many of those are grammatically animated. So you can like "czerwonego tulipana" (red tulip)
Oh, you're right. Some fish have masciline names and other have feminine names. So while buying an aquarium fish, one could say, that he wants "czerwonego gupika" (a red guppy) or "czerwonego bojownika" (a red siamese fighting fish).
It could be correct, if there is an implied subject, which is plural:
- "Nie lubię żółtych butów..." -- "A lubisz czerwone?" [ I do not like the yellow shoes... -- And do you like the red ones?]
- "Chciałabym kupić ładne róże do mojego ogrodu" -- "Lubisz czerwone?" [I would like to buy nice roses for my garden. -- Do you like the red ones?]
It could be in context.
Lubicie czerwony (kolor) Do you like colour red.
But in context, we can discuss wine and ask Lubicie czerwone?. I cannot imagine other examples (feminine)
So when talking about colors in general I have to use masculine gender, right?