The general idea is, the lighter the hair is the less chance laser has to successfully remove it. With that said, I have several white hairs left that still get's zapped by my laser, and the laser still targets it just fine, turning it a dark black because it's burned.
Laser technology has come a long way, but if you're hairs are mostly white or clear, then electrolysis is your best bet.
My suggestion is to try a test spot or if you have the money to spare, do a full treatment and see what kind of results you get. My first treatment killed off 60% or so of my facial hair. So you will certainly notice if it was successful.