Arcade
A large palette offers many hues, but neighboring areas also need a visual relationship that makes the picture readable.
Choose an important boundary
Best Coloring Book describes fifteen pictures and a palette of one hundred twenty colors. Before selecting several attractive swatches, identify a boundary in the current image that you want to remain clear. It could separate the subject from its background or distinguish two adjacent parts, depending on the actual illustration. This gives your color choice a local purpose beyond using a different hue in every available area.
Compare light and dark as well as hue
Two different colors can still look similar in brightness. When choosing for neighboring shapes, inspect how clearly one stands apart from the other. A lighter and darker relationship may help a boundary remain readable, while a gentler contrast can intentionally make an area feel quieter. These are creative choices, not a rule requiring maximum contrast everywhere or a claim that the game includes a numerical brightness tool.
Check the boundary at the picture's normal view
After applying colors with the actual pencil, paintbrush, or bucket tool, look at the whole image again. Does the important boundary still read as intended when you are no longer concentrating on one small patch? If the shapes merge more than you wanted, reconsider one neighboring choice rather than replacing the entire palette. The exercise is about the relationship between adjacent areas, with the available colors serving a clear visual separation or a deliberately softer transition.