Who says that leaves are green

[Cassiopeia88]

Who says that leaves are green
Or sky is blue?
Who says that days are always light
Or night is immanently dark? <==== spelling error. Should read "imminently". Actually, it is immanently in the sense I meant, like inherently: http://www.dictionary.com/browse/immanently

Who says what anything is really like?

Who says I have to be like you?
Who says you have to be like me?
For your green may be my blue
My light may not be light for you   <===== I don't know if you were going for a rhyming couplet or not but if you were, I  would tighten the meter a bit. For example changing the second line to "My light may be dark for you." If you weren't shooting for a rhyme, you may want to change one of these. For example using indigo instead of blue (and yes, I know indigo is not a shade of blue but I think it would still fit the colors metaphor you are using here). I wasn't, I'm terrible at rhymes anyway

… and my colors change as seasons go.  <=== I can't help but feel this ends a little abruptly. Maybe something like "as seasons pass away" or "as seasons fade away" would be more appropriate? I guess fade away would sound better, I like that.