Hi, I'm going to do a program who let to detect if a graph is planar or no. The program runs very well. The goal of this first stage was to have planar graph to color. Indeed, this graphs have got particulars properties which let to color these with better algorithm than classical graph. So, I must find an algorithm using this properties. The problem is that I don't arrive to know how to begin in my algorithm. What properties are the most interesting for the coloration ? (I know a planar graph is 5-coloriable, but I don't see how use this in an algorithm in fact). If someone had an idea or a link on the web, I would be interested. Thanks to you. Sylvain.