Color and insulation

In general, black absorbs more heat, white reflects more heat. So the black-colored surface is generally going to be warmer than the white-colored surface. I'd be really skeptical if someone told me they could notice the difference in warmth between two different color jackets, though. Generally speaking, we're talking fractions of degrees. On a very sunny day I'd speculate that the surface temperature of a white jacket might be as much as a full degree cooler at most than a black jacket, but when the sun is not out, the difference is much less pronounced.

However, I think something like red or dark orange color can have a definite psychological advantage over blue or white. You're likely to feel warmer in a jacket the color of fire than in a jacket the color of ice, IMO.

I've never believed that the inside of a sleeping bag's color makes a difference while your inside it. I think there could likely be some physical differences in the material, but I don't think the color itself would matter if it wasn't exposed to any light, whether it was night or day.

When exposed to radiation source like the sun — sure, black will absorb more and white will deflect more. But when YOU are the heat source in the middle of the night, I doubt colors will make any noticeable difference — unless you radiate visible light…

"unless you radiate visible light…"

I've never been very bright. I guess that's why I'm such a cold sleeper and need a bag rated for 20 degrees less than the nighttime lows. :-)

"unless you radiate visible light"

Good point, but it's worth noting that materials which absorb and reflect in the IR spectrum do exist, they're just not widely used in clothing. Actually, I have a New Balance down jacket that uses an aluminized inner fabric which they claim can reflect some body heat back onto your body. It's hard to say how well it works because it's integrated into the jacket, unfortunately, but it's a similar concept as the space blanket.