The opposite of pink is red, roses are red, my eyes are rose red, my pony is pure black. He is the exact opposite of pinkie in colors
That doesn't make much sense.
On the color wheel-- Um... Hmmm... Color wheel doesn't have pink on it.
The opposite of blue is orange, though, so she'd have orange eyes.
If I take Pinkie's profile picture and Invert Colors in Paint, she turns green (kinda like an asparagus, with her mane being the leaves) with orange eyes. She also turns a little demonic-looking, yet still.. cute.
.... *Facehoof* Duh. Green is the opposite of red, and pink is a derivative of red and white.