Design for the person holding the page
Give the main subject room to breathe and keep the smallest areas large enough for the intended age group. Use a white background, consistent outlines, and margins that will survive a home printer. If a decorative element does not help someone choose a color, remove it.
Check elements and file settings
Use outline-style artwork or line art that you created or licensed. Preview the design in grayscale, inspect the edges at full size, and export as PDF Print for paper or a high-resolution PNG for digital use. Keep the editable design as the source of truth.
Make one proof before publishing
A physical test catches faint lines, clipped margins, and details that are too small to color. For a broader look at formats, page counts, and publishing decisions, read the coloring book guide.