Colours, those are really wonderful thing. However getting colours to look realistic is not really that easy, you can't just pick bright red and say that is colour of curb, it takes really lot of work to get colour right.
This work is quite often not done with rFactor mods, colours jump to your face, well kind of, everything looks like they have came off from children's movie or something like that. In reality there is so much more variety in colours but still they tend to be less bright when you compare what you see in rFactor.
Someday I hope that I can start working with colours a bit, it annoys me every day more and more how wrong some colours look in my mod, how ever it is not easy task to learn how to use colours and then to find proper ones, it takes lot of time, maybe I'm ready by time S3 final of LFS does arrive