Not unless your MacBook gets red hot.
See:
https://www.europhysicsnews.org/articles/epn/pdf/2007/01/epn07102.pdf
"Black" objects do absorb and radiate heat more efficiently (the two things run together), but it is only significant if they are "black" at the frequencies emitted at the temperatures involved - which you can't tell just by looking at them in visible light.
Visibly black objects
do get noticeably hotter in sunlight because the "temperature involved" is that of the
sun which emits a lot of energy as visible light. For objects at ambient 'earthly' temperatures ~25C, most of the radiation is in the far infra-red, so the visible colour of the object makes no significant difference. Turns out that - at those frequencies - pretty much
all paint is "black".
If you look at a
table of emissivity (1=theoretical maximum, for objects at room temperature) you'll see that polished metal has very low emissivity (polished aluminium = 0.07), anodised aluminium is
much higher (0.77) and most types of paint are in the 0.8-0.95 range. So yeah, paint your heatsinks and radiators
any colour you like because any sort of paint or coating has far higher emissivity than bare metal. I think Macs use anodised aluminium with pigments added - probably even to the 'silver' ones - so my guess would be that all modern Macs will be about the same.
Also, since we live in an atmosphere, in most cases convective cooling is far more significant than radiation, so airflow and surface area are far more important than radiation. Unless you're dealing with 6000K sunlight - and your "midnight" Mac
will get hotter than a silver one if you leave it in the sun.
