Hi t_w, is this for a one-off or for a production run? If it's for a one-off you're almost certainly going to find anything other than 3D printing prohibitively expensive, although 3D printing (unless very high quality) is more likely to be the least long-lasting and lowest quality, so it's a trade-off. Either way, you'll probably want to 3D print the initial versions to check their dimensions, etc before going to any other service. If the keys are anything like the sort I've seen over the years, it should be fairly simple to produce a 3D model and Blender is really using a sledgehammer to crack a nut. With simple planes like this 123D Design would be fine, or pretty much any of the free simple modellers, though of course "simple" is defined by experience.

Colour shouldn't be a problem for any process, although for 3D printing it could be a moderate pain changing the filament so often, but that depends upon the printer.