Multicomponent thermochromic systems have potential applications in rewritable printing materials. A hindrance to the widespread application of these materials is a lack of detailed knowledge of the intermolecular interactions within the systems. In this study, dye–developer interactions from a typical three-component (dye/developer/solvent) thermochromic system are examined. The stoichiometries of stable and metastable dye–developer complexes formed are examined and thermodynamic interaction potentials are determined. The colour-forming interaction and its importance to the understanding of thermochromic multicomponent systems are discussed.