I've been thinking about doing a translucent blue themed keyboard, and I have a pile of matias and gateron switches laying around (also some lab surplus glassware and a stirring hotplate), so I thought I'd try dyeing them. I used RIT liquid dye (navy), mixed with an equal amount of water, at 45-50 celsius, stirred constantly.
The gateron switches became pretty dark after about 30 minutes, and slightly darker after 60 minutes. The matias switches didn't take on any of the dye, even after two hours. Ultimately, the gateron switches ended up a bit darker than I wanted, and using shorter times would probably only make the color inconsistent or not penetrate deeply enough. Also, disassembling and reassembling many switches would be a pain. Conclusion: maybe worth it, might be better with other/lighter dye colors.