The schematic views for metro maps are used to maximize the transmision of relevant information (lines, metro stops) of network visualization. Automatic generation of metro maps focus primarily on the physical structure of the network, but little on the choice of colors which is an accurate visual discrimination. In this article, we propose to invesigate the generation and placement of colors to be assigned to lines of a network. The first step is to find as many colors as lines of the network. These colors must be perceptually as distant as possible, and available in the vocabulary of colors. The second step is to place these colors so that the closest lines have the more distant color. The positioning of colors is a NP-complete problem, thus we use a meta-heuristic approach to solve it. To validate our method, we apply it to the field of air traffic control with the maps of Flight Routes.