Here's how I see the colors:
White - simple, basic, clean. You could definitely dress this color up with different accessories because it's neutral.
Blue - the most common one I see. Looks very nice, not too bright.
Green - it's one of the brighter colors (if not the brightest). Definitely attracts more attention, looks very nice as well. Haven't seen any in the wild.
Yellow - pastel. If you like more subtle shade of colors, this one is the top contender. Also looks very nice.
Pink - um... I don't like this color. It looks like ketchup mixed with mayonnaise (it's a delicacy in Puerto Rico

) but this color is overall the worst looking one to me. (Don't attack me)
Between your 2 choices, I'd choose green.

blue is just too basic and I've seen too many people with them. (Kinda loses it's charm after seeing literally 100 people with it.)
It's all about personal preference, first ask yourself, 'will I get tired of this color?'
If the answer is no, go for it. I doubt it will be yes.
Enjoy your 5c!