Neil, I personally wouldn't bother changing the colour of the splitter. If you get a Scott Lowe one then it's matt black finished anyway. In fact I think most companies finish them in matt black. With it sitting so low to the ground it will be easily chipped, so just leave it the way it is.
You'd honestly have to get down right next to mine to notice it was a different colour from the car.
I actually think most non black cars look better with the black splitter too.