I created a new blank project, insert a basic sphere into the scene.
When I switsch to Paint mode an select Color View Mode to RGB the hole scene becomes black.
I can not paint with white nor do the fill option works.
In 4.19 it works like it should. Also when I migrate from 4.19 to 4.22.
ue4 material usually works fine in progression with ue4 versions
but sometimes u might wanna remake the material
also make sure both sphers from 4.19 and 422 has the same polycount because low poly count doesn’t work with vertex painting.