I searched for other skins but couldn't find a skin that changed this color Can't I change this color?
There is a file called citybus_main_c.data.dds which decides which parts are colorable (white) and which not (black). (Keep in mind it's not the same for all other cars.) You would have to make a copy of this file and color the part where the bumper UVs are in Blender, then it should be colorable. If you want to just have a different color and not colorable in paint selector, do the same but with citybus_main_b.color.dds instead.
Im just goint to do the citybus_main_b.color.dds but which part of the file actually is the bumper because i can't find it
oh i get it now but i tried to change it to a different colour by changing the citybus_main_b.color.dds but it didn't work this is the image i wanted to change the bumper to