Fastness measurement by eyes is subjective, since it is dependent on evaluation of the observer. Sometimes problems occur because the producer and customer give different values to the same fastness test. To eliminate subjective perception of evaluating colour fastness by eyes, instrumental colour fastness measurement methods have been developed and it has been presented to the service of textile sector. The aim of this study is to evaluate acid and basic colour fastness to perspiration and colour fastness to washing of reactive dyed cotton products both with the eye and spectrophotometer. To make comparison between visual and instrumental results, developed PF/3 factor has been used. The highest PF/3 value was 12.35. This shows that the instrumental and visual evaluations of colour fastness tests exhibit 87.65% agreement even in the worst case.