The WindowBlinds 7.19 beta introduces per skin colouring settings.
Basically this means each skin can add its own custom colours to the colours tab rather than having to have multiple recoloured presets for each substyle that the skin has.
Skin authors can create each colour preset by using the usual preset saving options in the WindowBlinds UI and then find the .WB07 file and make a copy of it and change the extension to .WBC7
Once done the colours tab should show those custom colours in the scrolling box.
You can then delete the colour presets from the .WB07 file using the delete preset options in the WindowBlinds UI and you now have all the custom colours applied to all of the substyles your skin has.