I am trying to find some evidence against multi-colored navigation links, however it seems to be surprisingly hard to find.. perhaps not so many people have come up with the "innovative" idea of coloring navigation buttons with varying colors.
Also, if someone thinks that this is a great way of visualizing navigation buttons, I would be curious to hear that too.
In my opinion, the main problem here is that it is difficult to figure out which button is selected. The buttons stick on the screen and are used to indicate the selected option. I think this is pretty much common sense, however, some people I am working with on this project to think it is a "matter of taste"