When you were dragging it around, it was changing color. I know the color is supposed to change based on the heat, but why was it changing when you were dragging it around?

It's actually not changing because I'm dragging it around. You're just seeing the color change a bit more, because as I move it, those particles are spawning continuously. So at the start of each particle's life, it's blue. So this just makes it more clear.