Here we have a plugin that makes your life much easier → Plugin: Theme Creator Extension there you can address the elements whose color you want to change directly via its input mask.
But otherwise it is true, in these *.colors files can be a lot of values that aren’t available in Krita since this file format stems from / is for basically all and any KDE applications, and you can customize whole KDE desktops via this format, so if you are searching for a documentation on this, you have to search in that direction.
So the group KDE will be for the whole desktop I guess and WM is the usual abbreviation for WindowManager.
Michelist
Add/Edit: Also guessed, BackgroundAlternate will probably be for selected items like a selected layer gets a new background color.
Add/Edit 2: Also this will be helpful for a deeper search on the roots of this: Plugin: Theme Creator Extension - #10 by freyalupen, and I don’t know if you already found one of my posts about more sources for color profiles, this one for instance: More Krita themes that go hard - #16 by Michelist → and there you should follow this link to get access to thousands of ready-made color-schemes: KDE - pling.com