Hi
If you are not comfortable tweaking the rtconfig.txt file in the unpacked theme you could have a look at the theme tweaker in REAPER.
You access that by opening the Action List,
Actions > Show action list...
and then when the Action List appears, type "twea" in the filter text box.
That will present you just one action, Theme development: Show theme tweak/configuration window
Double click on that, or click on the Run button and you a window will pop up. Within this window you may be able to tweak some of the background colours to suit your colour blindness.
I can't say whether it will or not, but it is worth having a play with that.
Once you have something usable you can save your theme from that window.
cheers
andy