|As a disinterested party (i.e. would never use the software) but interested in GUI design, my 2c
The tabs in the control layer seem to be ok , not too many of them and the contents look like they're obviously related - but I can imagine a user having to switch between tabs frequently while they play around with colours.
You seem to have two panels headed 'select Paint System' on the General tab, which may be confusing
Personally, looking at the form layout, I would probably make each of the user controls (for I assume that's what they are) collapsible and and re-positionable, and have only one tab (plus maybe the info tab - you don't show that in the screen shot so can't tell)
That way the user can collapse any controls they don't want to see, and drag controls to the top for those they do want to see and use 'right now'
You could also allow them to be re-sized, avoiding the need for scroll bars on some of them...
Then if you wanted to be flash you could have them dockable - so the user could drag them out into their own windows...
It'd make a nice article too - generic dockable sortable collabsible and draggable user controls...