I've tried putting colors on the visor to make it a rainbow color, but when I go into the game, I get them same black visor. Can someone help me by explaining how to change the color?

iirc the visor colour area only changes the reflection colour slightly, rather than colouring the whole visor, i.e. it's far more subtle than a coloured visor.

The visor's polygons have a polygon colour, overtop of which the skin is diffused. The visor colour is a very dark grey, so any colour you put on the skin will be visible, just very, very, very dark to the point of being nearly non-existant.

There is a little area on the bottom right of the master skinnerz template with wich you can (some what) color the visor.