A mess-free coloring system comprising a coloring medium and optionally one or more coloring utensils is disclosed. The coloring medium can include a substrate with or without decorative effects and one or more coating layers on a surface of the substrate. In various examples, the one or more coating layers include a color-triggering developer, e.g., in the form of a substantially clear resin, and an opaque pigment. Decorative effects integrated with or disposed on the substrate, while initially obscured by the one or more coating layers, can be revealed when the coating layers are mixed with at least one color precursor stored and dispensed from a coloring utensil. The opaque pigment is selected and configured such that, upon receipt of at least one color precursor by the one or more coating layers, a change in the pigment's reflective index occurs as the pigment dissolves into the clear resin developer.