Crossword Genius

It's blue, green, or maybe Red (3)

Ross

I believe the answer is:

sea

I'm a little stuck... Click here to teach me more about this clue!

'it's blue' is the definition.
(thesaurus)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for sea that I've seen before include "The main" , "The tide" , "Body of saltwater" , "one may be pounding the beach" , "& 14 Ozone" .)

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