Abstract Achieving drastic color tuning in nanophotonic devices requires nanostructures optimized through a deep understanding of light‐matter interactions, including resonance wavelengths and their associated electric‐field distributions. This study rigorously investigates heat‐assisted nanoparticle rearrangement to achieve precise color tuning. A Fabry–Pérot (FP) etalon is proposed, comprising multi‐layered metal–dielectric–metal films, plasmonic nanoparticle assembly, a fluoropolymer dielectric, and a metal mirror layer, enabling nanoparticle‐behavior tracking at visible wavelengths. Through controlled experiments and simulations, the roles of physical elements in the FP etalon are investigated, particularly the optical cavity thickness and the filling fraction of the top layer. To enhance color variation through the dynamic behavior of nanoparticles during successive heating processes, a flowable polymer film is prepared as a dielectric layer, and color tunability is systematically examined. The investigation focuses on the heat‐assisted dynamic behavior of nanoparticles, including the submergence and coalescence of gold nanoparticles, along with the simultaneous shrinkage of the surrounding polymer film. Based on the results, laser‐mediated local color tuning via the photothermal effect of gold nanoparticles is performed for potential application as a color printing technique.