It seems that the paint tool does not show which 'target' (primary, trim 1, trim 2 etc) and which color palette slot are used for a particular segment of a particular part.
This means that changing the color scheme of a vehicle is a tedious time consuming process of trial and error: To find out which color target and color slot is used for a particular segment of a particular part, for each segment of each part one must select a color target, select a color palette slot, then click on a part to see which segment of that part changes to the selected color.
And because the player will probably not memorize which color target and color preset are used for a particular segment of a particular part, this must be done every time one wants to change the color scheme of a vehicle.
suggestion: The paint tool needs a 'color picker':
with the color picker active, the paint tool would show which color target and which color palette slot is used for the segment of the part that the player has clicked on. Then to change the color of that segment of that part it is a simple matter of selecting a different palette slot and/or adjusting the color of the currently used palette slot.
@bspawn ok