The use of color is indeed fantastic. Except for choosing a black background for the graphs.

I wanted to print the webpage wihtout wasting so much ink. And a white background improves readability too.

For that I needed to learn how to manipulate the image in order to invert only the greys without altering the rest of the colors. It actually was pretty easy with Gimp (duplicate layer, choose mode: HSL Color for the upper layer, invert colors for the lower layer).