The purpose of the study was to verify whether increasing the content of tyrosine and phenylalanine in the feed would result in more intense colouration of chinchilla fur and affect the animals’ reactions to behavioural tests. Chinchillas were divided into 3 groups: G-1 fed complete commercial fodder (Tyr 6.91 mg/g, Phe 7.45 mg/g), G-2 fed commercial and experimental fodder (1:1 ratio), and G-3 fed with experimental fodder (Tyr 14.31 mg/g, Phe 21.65 mg/g). During the experiment, the fur colouration type was assessed using two methods: objective, with a colorimeter (CIE L*a*b* colour space: L* – light-dark axis, a* – red-green axis, b* – yellow-blue axis, C* – colour saturation), and subjective, by a qualified chinchilla judge. A behavioural hand test was used to categorise the chinchillas’ responses to human intrusion into their cage. The results from the colorimeter measurements did not show any significant differences in the L* (P > 0.05) component; however, significant differences were observed for the a* (P = 0.0029), b* (P = 0.0218), and C* (P = 0.0342) components in relation to the fur colouration of individual groups. The assessment of the colour type by a qualified specialist found statistically significant differences (P < 0.05) between the initial and final measurements. Spearman’s correlation coefficients between colour type assessment and colour components were mostly low or medium, but with stronger values observed for L* compared to a*, b* or C*. There were no significant effects of the feeding group on the results of the and test. However, a decreasing trend was observed in the hand test results for G-3 from week 5 of the measurements