Bavarian pilot Captain Joe described why airlines paint the nose cones of the planes black back in the day. It turns out, that “radome” is where the weather radar is placed. A black rubber cover was practiced to protect that dome and the sensitive equipment inside from debris abrasion. The rubber sheet was only short-lived, as the airlines then switched to much less costly black paint.
Later, airlines stepped away from the rubber coating and then painted the noses with black paint. Back then, the fuselage was covered in lead-based paint to prevent corrosion but wasn’t allowed to be sprayed over the nose due to the metal compounds of that paint. So yet again cheaper black paint was applied without interfering or limiting the Radar’s performance.
Modern airlines have stepped away from the color black and have got colors more in line with their airline logos.
Eventually, that colour range grew more and more, and airlines painted their planes in their colour of choice to match the livery!