As I understand it they were black according to regulations. However; due to supply problems some were made in infantry khaki. And I think some were cut in a dark almost navy blue as well. Far as I know they were the same in cut only the colour of the cloth being different. And you can mix and match black and khaki uniforms between the members of a tank crew as well.

I understand the helmets varied in the shade of the leather used too- most being black but brown leather being used in some.

Here's a set of tank commander's coveralls (worn over the uniform or by itself) and kit. 

Thanks gents, epecially for the pic.  I'll go with the black.