You can actually paint the keys black. Run the keyboard keys through the dishwasher. YOu can then plug them back into the keyboard.
As for the paint, use automotive paint as it actually bonds to plastic, some colors don't even require primer. I've used krylon, but their nozzles are sub par. I use an airbrush and compressor, it provides such a fine stream that a spray can could never match.
To relabel the keys you can get white water slide decal paper and on a PC or MAc in Adobe illustrator use a cool foont like Eurostyle or CGFURUTA and type out the keys. You want white keys on a black background.
The waterslide decal works like the model kits out there.
Then use testors dull cote or another MAtte or satin finish. To match the Amiga keyboards a little better use satin finish.
I ran a model shop paint dept for 10 years. Works like a charm.
Now what's this I hear about using die? I thought about using india ink as a base as that stuff is impobsible to get out.