Makes perfect sense
Graphs are meant to help viewers visualize the significance of a certain phenomenon. The viewer is supposed to draw meaningful conclusions with basic information displayed on the graph. However, if you use confusing colors and labels, you can bet that nobody will understand what point the graph is trying to make.

Here, white is portrayed in blue, blue in red, yellow in yellow, black in green, red in orange, gray in turquoise, and brown in blue. Makes sense, right? This person could have color-coded the graph to coincide with the color of the label, but no. That would make it too easy to understand!