Sorry I should have explained how to set those up
At least I can give you another tip?
If you find a color that your working on isn't quite right you can change it everywhere with the paint bucket. Set the tolerance to 0, unchecked anti-alias, and unchecked contiguous to change the color everywhere on that layer.
P.s. the article I saw on making a preview window had it tiled with your project. If you want a free-floating preview you can move around, do window-arrange-new window then on the new tab of your picture go window-arrange-float in window