I have seen some black interiors. It'll be hot, but I'll bet you couldn't tell the difference between black and other colors if you take temperature measurements. With a bubble on top, it just gets hot! My -6 had grey seats and if you left the plane in the sun with out a cover, you couldn't sit on them. (As you probably know, cloth seats are better for not getting hot than leather or vinyl.)
Black has other drawbacks...it makes the interior look darker and smaller and if you drop something small, it's tougher to find, especially in flight.
For me, it's just personal preference. I have always liked to use black in conjunction with other colors. For example, paint all of the roll over structures, pedals and sticks black. Use black carpet and maybe stick boots and then use a contrasting color for the seats and panels.
Again, personal preference, but I do believe black is easier to touch up when you get nicks and scratches.