With the advent of radar, the protective black nose cone coating not only served to lessen damage (from ice/hail, birdstrikes, etc) but was of a compound that that did not interefere with radar ops as other coatings (read: paint) would. The black "radar nose" stood as a status symbol and some airlines even advertised "radar equipped" with a photo of the black nose of their particular aircraft featured prominently in ads, timetable covers, etc.
With newer protective compounds and "decal" technology eliminating most (all?) of the above worries, plus "radar equipped" is a given now, I think you'll see more carriers retiring the black nose, IE
: going to a more analogous grey, or even carry their livery color(s) through the nose cone.
Second paragraph above is only my opinion; I could be 180 deg. off-base, here. Regards...Jack