Now I can print very precise color on Cherry MX OEM profile keycaps. (Not for Model M keycaps, sorry)
I made a general solution. You can use it too. It is very good for common photo printing too. Do your printer and its ICC profile play like this?
Moreover, you don't need a colorimeter for the solution. Instead, just a flatbed photo scanner.
It is an online service. What you should do is, download, print, scan, and upload.
The solution is Zygomatic Color.
Spend $50 get your ICC profile!