Hmm. My area used to use gray FP Sun-Tech photocells, but they've been using black PCs recently. The black ones are 120 volts I think. I know the gray ones were 120V.
Actually no. The ANSI standard colors are: Gray is for 120v, Blue is for 120-277v, Maroon is for 208-277v, Green is for 347v, And yellow is for 480v. Black is a special order color. You can order black on any voltage photocontrol. And actually, you can order ANY color for any voltage. I once ordered some 120-277 volt photocontrols from DTL with gray covers.