painting a frame is possible, you have some recipes like sand, remove grease, spray vinegar, paint, sand lightly then paint one more time.
it can last longer thant you think.
Painting keycaps may give you some uncertain results.
The RIT dye has the best results (US only, i can't find them in France, and inmost parts of Europe).
One other solution is the fusion paint from krylon http://www.krylon.com/products/fusion_for_plastic/
there is a dealer in the UK. Not tested yet.