Feather color varies among individuals within a species and it is important to understand what can cause these variations to occur. In great tits, there is variation in the coloration of the feathers on their breast. The yellow coloration of their feathers comes from carotenoid pigments obtained through their diet. Through spectrum analysis and visual modeling, I have found that some of the variables that relate to this variation in feather coloration include sex, age, habitat, season, bill length, and skull width.