Aluminium PCBs usually have white/black silk screen without addition costs. This really gives nice panels.
Just consider that the insulation layer in not stripped when removing copper...
I also did fr4 wif black/white silk.
Works nicely as well and looks pretty

This usually costs a little more than standard green.
For early prototypes I tend to use green FR4 panels... This gives me some visual guidance on the HW revision. Very helpful when you have several revisions on the shelf.
Regards