To start with this is a big undertaking! Getting to the keyboard is not easy to even get to the keyboard LED's. I wouldn't spend the effort just to be cool here, just taking the system apart can be risky in damaging something.
OK, I've warned you! So what would I do?
If you have a bad keyboard so you need to open it up to replace it then I could see altering the coloring as something cool. But instead of trying to change out the LED's how about just coloring the white LED's with a dry erase marker with the color of your choice.
As to the LED's them selves they are fixed color (so you can't program them and altering them will only allow you to switch out to a different fixed color LED which I think is just not worth the risks, besides you're then limited to that one color.
The wiring of the keyboard does not offer a means to use a multi-color LED so it could be altered from one color to another. With that said it would take quite a lot of engineering to design and manufacture a replacement keyboard and then have a way to control it. Sadly, I think your just reaching beyond what is practicable here.
Why don't you order a replacement keyboard to dissect so you can see whats involved and whats makes sense.