You're right about the default specularities... interesting. I stand corrected.
But I have to still disagree on one point; light does have color... sunlight is all colors, mixing into pure white. You can filter out other colors to achieve an effect, as in a sunset (which I believe AH simulates by changing the global diffuse values). And, as you say, you can change the ambient lighting by bouncing light off a large red object... but you can't plan to simulate that ambience for every possible setting. In that case, white would be more appropriate.
Yup, lots of experimenting to be done.