That is a nice suggestion to try.
In OS X, the color maps get put into a directory called Application Support which is a good place for such things.
However, rather than put them into the Application Support directory of the System itself (which would be something like /Library/Application Support/REAPER/Data/color_maps), they are being put into the Application Support directory of the currently-logged in user (such as /Users/paul/Library/Application Support/REAPER/Data/color_maps)
This may be a permissions issue where it was easier for HMX to make their RBN Tools installer script install into the user's directory instead of the system directory which might have required admin rights or something.
Or maybe it was a conscious choice where they wanted each user account to have its own copy of this stuff.
I will make a test user account on my laptop named exactly the same as the one on my tower and see if that does it.