It seems to me that the Japanese are very 
fasniated...not, per say, with the "Western" 
look, although that does appear, in a 
caricturized form...more like, with a "different" 
look. Think about it..every native Japanese 
person has got pretty canon coloring...dark hair, 
dark eyes. Granted, there is a lot of leeway in 
this, lots of different shades, but it is nowhere 
near the melting pot we have here in America. It 
seems to me that they want something different, 
something unique. Not to mention eventually 
character designs would get very boring ^_^ (not 
as to say Japanese faces are boring and all the 
same...but since anime characters really have no 
detail on their faces except the basics, it's 
sometimes hard to get characters to look 
different, which is when different hair and eye 
color helps to set them apart, whereas if they 
were colored and looked like real Japanese 
people, it would get monotonous because it's hard 
to put detail, like the subtle differences in a 
way one person's head is shaped differently form 
another, or the way their cheeks bunch when they 
smile, etc.). Yes, I know some anime do have 
people with "real Japanese coloring", but even 
then those people are caricatures, and some have 
the larger eyes, or else they all have beady 
eyes...
Basically, I attribute it to a taste for 
something different (and the fact that anime 
designs would indeed get boring...not very 
profitable, ne?)