RGB Preview Colors are wrong, Buggy touch of red ?

Hello together,

I am doing a  hardware color mixer and  I already brough tthe RGB Values over seriall rs 232 Por to grasshoper, works fine,  I want to controll the colors of the mesh of the car... well it works but the problem is there is a buggy touch of red even when it should be blank withe with R:255 G:255 B:255, also when i put the color slider for total Black

R:0 G:0 B:0 its a touch of violet...so there is something wrong in the preview...

Can somoene  help me !!!

Thank You

Raph