 You just stated it. It's because they do absorb heat because of the color of their fur. I've pet both a very fair-colored dog as well as a dark dog in the same temperature, and I can definitely feel that heat. Now, a lot of people like to shave their pets during the summer to help things that help them, but it doesn't because that fur actually insulates them a little bit against the heat. So the answer to your question is yes. I think the darker the color, the more susceptible they're going to be to getting hot. That's just common sense.