As far as noticed, at least PiTool .086 doesn’t work properly with the individual colour correction: It doesn’t consider the colour-specific value additionally to the general all-channel-settings, but internally first reverts the all-channel-setting to “0” and then applies the colour-specific value.
Probably a bug, I cannot think this is intended on purpose.
Imho, the contrast and brightness slider GUI need an overhaul, i.e. all four sliders (all channels, blue, red, green) one below the other at the same time, so one can adjust them one by one, but having all of them in sight. Clicking “apply” then applies the setting as a whole at once without having to switch between the colour tabs and loosing context, both from user side as well from application side.
Just my two cents about it…