Welcome Ted

Dealers will say anything to close a deal, so lets look at the science.

At the molecular level, different colours have different surfaces, with different drag coefficients. So two colours will cause an uneven drag over the machine, thus affecting the aerodynamics.

Now as for colour, we all know that visible colour is reflected out of the light spectrum, the rest having been absorbed, so black means that all light has been absorbed.
So the following equation proves black is the fastest

Light = Energy
Energy = Power
Power = Speed

I rest my case

Too old to die young, too ugly to leave a good looking corpse