I've been running into a possible bug - My gold dwarf pc has been affected by color spray numerous times against evil npc's while having PfE up.

Are you sure they're evil?

They were gnolls. The others in my group weren't affected the first time, either.

How many HD did your character have? If below 5 HD, then this is completely intentional.

Depending on your HD, colorspray has different effects.

If you're the HD that gets you the blinding effect, I think it doesn't count that as a mind spell and thus PfE doesn't ward against it.

I've my doubts that this is intentional all the way:

If you have below 5HD and you use PfE, you do NOT get ANY save against Color Spray at all. Automatic fail.

My gold dwarf has not had any issue with getting nailed by a color spray and PFE so far. Not sure if that helps.