It should be don't move and match the background color. We should probably provide a way for background color to be changed in some areas of the simulation by the user (or allow bots to see the color of the background pic! That could be really cool!).
Color change via muatations should be included. Every cycle you're changed from your regular color costs energy, and as you get closer to the background pic (like within a few values of red, blue or green) you begin to be seen less and less by other bots. Like if you're off color by a bit other bots can only see you 95% of the time. As you get closer in color, bots see you less and less often. Provided of course you're not moving.
And, before Carlo makes the point, this camouflage color and the color visible to the users now need to be seperate. On some level the color the bots are is just a handy visual representation, so we should have all this other camouflage color stuff be seperate, and allow the user to switch between view representations.