You joke but it's interesting to think about what mixing them or mixing their components would do.

Mixing them as-is would ruin the effect of Vantablack. Since carbon nanotubes are black you probably would get a boring grey color with a gloss surface due to barium sulfate.

I'm curious what the effect would be if you coated Vantablack with barium sulfate. A highly reflective surface with an extreme black paint underneath.

"The paint mix, named MegaGray, reflects a jaw-dropping 50.000001% of sunlight."

I think what might be interesting is like two-sided louvers over your roof. black on one side, white on the other.

Flip from one side to the other to help maintain temperature by absorbing or reflecting sunlight.

The next step is using the combination in e-ink fashion, so that you can smoothly regulate the thermal profile as needed.

Genius. Just imagine.

Honey, it’s going to be -27°C (-16.6°F) tomorrow, can you turn the reflectivity to 0% after brewing the coffee?

You could probably more easily do this with just a flat surface that you can rotate. Smaller the squares the better uniform distribution you can get but if you don't have those strict requirements then why go super small (e-ink)?

Just need to make sure that the white coating doesn't block radiation of heat to the building underneath when black is facing the sun.

I'm assuming you would have put this on some conductive surface. Otherwise the black side wouldn't be super useful (you'd re-radiate heat back but conduction is better).

You could probably use a scaled-up version of the cable mechanism used in mini-blinds.

My next model rocket is vanta and superwhite. No room for shades of grey. :-)

Or the most extreme zebra.

The most jarring Dazzle camouflage[1] imaginable.

1: https://en.wikipedia.org/wiki/Dazzle_camouflage

Honestly I want to see this. Would your head hurt seeing it in person? Or would your eyes balance it out