Vincent, I hope that someone within the forum can give you better news than I can, or can provide you with something you need in that case. However i doubt that it might be possible to change the colors for the task stati.
Please also know that not only because of the color of a task the current status can be determined, it always goes with the Statustext, which can be also used to determine in which status a task currently runs. So if you cant determine it via the color, the text next to it is showing the definetly status in any case.