Honestly I don't pay attention to specific colors. A designer (I'm not) could answer the "too close?" question better. A great book for choosing colors is Color Harmony Compendium.

Although I don't pay attention to specific colors, I like having colors, they break up the tedium. I just think they're a poor choice for a sole differentiator. For example, I always like colors while programming in a text editor, but I never use color as an indicator for what I'm looking at; the code does that. :) Colors in a text editor just break up one thing from another a little earlier than my brain would anyway, but they never tell me what I'm looking at.