This document presents a framework for structure-preserving color transformations using Laplacian colormaps. (1) It represents images as graphs with Laplacian matrices that encode image structure. (2) It finds joint eigenbases of Laplacians to perform color transformations that minimally distort structure. (3) It applies this approach to applications like color-to-gray conversion, colorblind optimization, gamut mapping, and multispectral image fusion. The results demonstrate high-quality color transformations while preserving image structure.