I find it's really tacky when the eyeshadow matches perfectly with whatever top you're wearing. Like, baby pink top, baby pick e/s. Blech!
I usually choose a complimentary colour, or use the same colour but a different shade. Like if I'm wearing a light blue top, I might do a teal eye, or if I'm wearing pink, I'll do a lilac eye. I just think it looks better, and I always read in fashion magazines that it's a big no-no to match your eyeshadow to your clothing, and I agree.
But then again, I also wear a lot of white and black clothes, so I can really do whatever.