The colour change of Cu-13.8 mass% Al-4.0 mass% Ni and Cu-14.2 mass% Al-3.1 mass% Ni alloys was measured after annealing at 500 and 620 degrees C, and quenching from 900 degrees C by means of a recording spectrophotometer equipped with an integrating sphere. A large colour change of these alloys occurred on heat treatment, depending on the different phases of gamma’, beta(1), (gamma(2)+beta(1)) and (alpha+gamma(2)). The phase transformation between beta(1) phase with the DO3 structure, and gamma’ martensite with the Cu3Ti-type structure, occurred in the alloys. The phase transformation was dynamically observed by the change in the spectral reflectivity on the surface of these alloys during heating and cooling. A great hysteresis in the phase transformation was noticed in the spectral reflectivity-temperature curves and the premonitory phenomenon of the martensitic transformation was observed in the curves.