Adjusting When Reaper's Meters Change Colors

[Funkybot]

I'd like to tweak "when" the colors change on the Reaper meters. So not the colors themselves, but rather, at which db level the transitions occur from one to another.

For instance, I want to make sure I'm always leaving myself lots of headroom. So something like:

-inf to -15Dbfs = Green
-15 to -12Dbfs = Yellow-ish green
-12 to -6Dbfs = Yellow
-6Dbfs to 0Dbfs = reddish-orange
Clip = red

I know the Theme Editor allows me to change the colors if not a Walter .png image. But I don't know where/how to change the actual scale.