Btw, did you know that different colored speakers do sound different in a non-blind trials? There is a good, scientifically proved reason why speakers are black or natural wood colored...
Wel, the colour obviosly has no effect on the sound; some may say that the type of paint does, but this would be so insignificant that no human ear could possibly discern the difference. However, and this surprised me as well, the type of wood used can make a very big difference. The more resonant the material is, the more the sound will echo back; the phase difference is small, but it can be enough to keep transients alive longer, which will make more detail stand out. If there is too much resonance, the sound will get all distorted and sound like crap.
If you have a pair of open headphones, make a cup with your hand over the back of the cans; the bass will get significantly reduced and the treble will be accentuated. Reagrdless though, our ears get accustomed to whatever sound we're used to hearing, and even the in-ear buds that come with our mp3 players are good enough for most people who just want to listen to some songs.