I don't believe the color of shingles affect the cooling or heating of a house. I've read a few articles debunking the reflective barriers and paint, but never came across one on the color of the shingles. I think it's going to get just as hot in the attic during summer regardless of what color they are.
I prefer darker colored shingles. I also think they sell better if that's ever a concern.
More impotant the the color of the shingles is the quality of the paper and flashing. Just about every leak in a house if from the flashing. It's either not installed poperly, or old flashing is used again. Then the next thing that I see is they try to seal the flashing with roofing tar, which is fine, but only if the flashing is installed properly. Unfortunately I see the flashing is just next to the wall or chimeny, and the tar is supposed to act as a glue to hold it there. While it might work for a year or longer, it will fail fairly quckly.
The other thing is to make sure it's nailed down properly. I've seen guys cut corners and save nails be not using enough of them. I've seen them save a buck by buying short nails. I use 1 5/8 nails to make sure the shaft of the nail goes all the way through the decking. If the nail doesn't do this they will come out.
I hate staples on shingles. While the theory is that they are better, the reality is that they go all the way through the shingle too often and offer nothing to hold the shingle in place when this happens. Staples are cheaper then nails, but because of how often they do this, I would never use them or hire anybody who used them.
On the tear off, take it down to the decking. I've seen where they leave the old paper there, which hides any problems with the decking. If there is rot or an issue of some kind, the only way to know this is to see it.
Hope this helps,
Eddie
Eddie