Air temperatures inside the IC are usually much hotter than even the air under the hood,
at least with above say half throttle and when moving, So, what you want is heat to transfer out from the IC to the air outside. That is the reason why there is an IC. It delivers cooler thus more dense air into the combustion chamber than otherwise. The main mechanism is convection, heat flow by radiation is negligible. So the color of the surface makes no difference in practice.
Special circumstances - such as on a hot day when the vehicle is stationary, then you want max acceleration, if this is your speciality then use a water spray. This covers the IC with water which evaporates taking up the latent heat required from the IC by conduction and convection, again color is not part of it. The video just about found this tho' as Kato says it was not a rigorous test.