Coloring in general is bad for your hair, but not horrible or anything like that. You aren't supposed to shampoo your hair 24 hours prior to color, because it makes your scalp sensitive to peroxides. If someone has long hair, I cut that long hair first if they're wanting a lot off. Then I go on with coloring. If they only want a couple of inches off, I color first. When you color it, your ends are mor porus and damged anyway, so color usually grabs for dark colors and is uneven, or doesn't grab the color at all sometimes. Since you're going to cut that hair off, might as well wait until the end. Plus, it takes 45 minutes to process most color lines. So while the client is processing, you can fit another client in for a haircut, wax, style, etc. People just say cut and color, because it rolls off the tongue smoothly. "Color and a cut" is longer, we're all in the age of technology and what's fastest!