Thermal modification is a process that aims to improve some properties of wood, such as biological resistance, dimensional stability and color change, enhancing the value of the product. Additionally, it is an eco-friendly process that does not use toxic chemicals. The main objective of this work was to evaluate the effect of thermal modification on the wood color of two species, jatobá (Hymenaea spp.) and caxinguba (Ficus sp.). The secondary objective was to compare two systems of color measurement. The wood samples were obtained from sawmills in the municipality of Itacoatiara, Amazonas State, Brazil. Thermal modification was carried out in a laboratory oven with forced air circulation, at 180 °C for 150 min. We calculated the mass loss and measured the wood color before and after thermal modification using the Munsell and the CIE-L*a*b* systems. There was a significant darkening of all the wood samples tested. The use of the Munsell and the CIE-L*a*b* systems returned different colors for all species. The CIE-L*a*b* was more effective in detecting the total color variation of Ficus sp.