A very easy process:
1. Take a photo of your work, download it unto your pc, view it on a viewer(Microsoft Office Picture Manager) "zoomed out" . This way the photo is much smaller and the colors closer to one another and you see an error so much easier.
2. Now correct that error on your painting.
3. Take a photo again and go through the same process again. Repeat the process until you are happy with the color balance.
