You do not need to use every color in the palette. A few repeated colors can make a picture feel intentional while leaving room to experiment.
Choose a focal point
Open Kids Coloring and inspect the available picture and color controls. Pick one area you want to stand out, then choose two or three main colors for the rest. Contrast can come from light and dark as well as hue. Avoid treating the reference picture as the only correct answer.
Try one variation
Change the background or one large area while keeping the remaining colors similar. Compare which version makes your focal point easier to notice. With a child, ask why they chose a color instead of correcting imaginary details. If you want to keep the result, check whether saving is available; otherwise a screenshot may be the simplest record.