Colour effect is obtained from mixing different coloured fibres before the blend. In the production of melange colored textile materials, the incorrect prediction of fibre colors, which will provide the melange colour desired, constitute a major problem for textile businesses. In this study, an attempt was made at estimating the mix of fibre colours to obtain the melange colour desired before production. For this purpose, polyester and viscose fibres were used in yellow, red and blue colours. These fibres were obtained in different ratios, three colour mixes and 720 melange coloured bands. The colour values of these bands measured by a spectrophotometer were expressed in CIELab 1976 units. The Stearns - Noechel model was the basis for colour forecasting. A new approach has been developed for calculating coefficient M in the model. This approach results in each mixture, and a different coefficient M was calculated for all the wavelengths in the range 400 - 700 nm. Colour calculations were made using the M coefficients. The average colour difference between the colour values measured and those calculated were found to be 0.95 CIELab units. This result suggests that in fibre blends, estimating the colour of the Stearns - Noechel model might be a sufficient result.