Yep, found that and managed to change the values of the skin colours manually, but there's no reference to the attribute thresholds other than "low attribute", "normal attribute" etc.
These values don't seem to be collected from the game when changed.
Edit: Idk if this helps, but there seems to be no issues with the default version of the skin. It responds to all custom-set attribute colours and thresholds.
The attributeless skin seems to ignore all custom input, and always refers to the colours set in the tcs settings file held in the settings folder of the parent skin.