Plumage coloration plays an important role as a signal of individual quality. We studied plumage coloration in two Great Tit Parus major populations to test the hypothesis that coloration changes during the year without moult. As expected, the coloration of ‘yellow’ and ‘dark green’ areas in the breast and back changed with time but not the colour characteristics of the ‘black’ crown. This suggests that colours based on carotenoids could be more exposed to abrasion or fading than melanin-derived colours, although other factors could affect the patterns of change found. Our results show that effects of colour alteration could be important to the understanding of the potential for reliable signalling of different colours. Seasonal changes in plumage colour should be considered in future analysis of intraspecific variation in coloration.