It can reflect it out to space. It is possible to make paint the keeps things below ambient. Obviously you're correct, but only for things not facing upward. Upward facing things will bounce the energy back away from Earth.

https://youtu.be/N3bJnKmeNJY?si=drxjIM8U_MAcQLQH

The amount of folks who have melted their shitty low quality thermoplastic patio furniture with their sliding glass windows will always amuse me, but overall I don't consider IR radiation to be a big problem. Using a bunch of VOCs to paint everything and pollute a city would be though.

Ok, so don't paint it on any concave surfaces. Most buildings have flat or convex surfaces.

great video. Its wild that it is functioning as an IR emitter and just beaming things into space.

Ultimately, they can be, but there's lots of differences between them once they reach the bucket you buy. They have different adhesion qualities, but that could be addressed with an appropriate primer. They have different final finish surface requirements, which could be an issue for how the paint works. I remember seeing dragonfly-wing-style paint that was white when viewed perfectly straight buy blue when viewed at any off angle due to a microscopic vertical grid of blue walls. There may also be a required clearcoat component that may not be compatible between the two surfaces. Metal paint is also designed to handle the flex of metal where as concrete paint would barely be concerned about that but possible address crumbling instead.

Edit: and after reading the article, it's a radiative-cooling paint rather than a reflecting coating. Concrete has a much lower thermal conductivity so this may not be effective in transferring heat out of the concrete.

Metal paint is concrete paint. Microsoft paint is abstract paint. This comment is metaphorical paint.