The same is accomplished with a lighter background and a lighter forefront. The trick is to just make sure the images go together. There are exceptions to this rule as is shown in the second picture from my book Fashionable women, where the background is lighter than the forefront image but this seems to work because the sixties theme is captured throughout the photo, so it seems to work.
Then there is balance making sure that the images are balanced from right to left to top to bottom. I will admit I fell short on this with my earlier coloring books and this is something that is not easy to accomplish. The best course of advice I can give anyone about symmetry and balance is look over the image does your eye go somewhere other than the middle which is where we want it to go in order to take in the whole picture, if that happens to ask why, and take care of the problem odds are it has to do with balance that is usually the case for me.
Also, another pair of eyes helps, my sister has become mine and I have had to deal with some harsh criticisms including redoing an entire page. Well, that concludes going into symmetry and balance not sure it’s the most interesting of subjects but still a necessary evil when designing a coloring book.