[glhaynes]

Everything being the same color can easily lead to a feeling of being "in a maze of twisty passages, all alike". It's like gray dialog boxes that pop up more gray dialog boxes: technical users tend to have an ontological hierarchy in mind as they navigate so it's no big deal, but most people get quickly overwhelmed and feel lost/overwhelmed. [Not that I'm saying that simply coloring dialog boxes differently would necessarily help here! Just that them all being gray adds to the overwhelm.]

I strongly disagree that color aiding in use points to a larger accessibility problem — perhaps you just mean that if color is necessary for use you've got a problem (which I'd certainly agree with), but while I could get by in my everyday world with monochrome vision, I'm glad I have color cues all around me that aid me in distinguishing amongst objects quickly and with minimal effort.

[madoublet]

Yes, you are right. Color when used appropriately can improve the use of a UI. But, he/she implied that it was unusable simply because the icons lacked color. That is completely wrong.