The purpose of the thesis was to examine the effect of dyebath dilution on dyeability of silk and wool and the wash fastness of individual dyes in certain dyebath dilution ratios. Additionally, the aim was to create a colour chart that would serve the designer as a guideline when dyeing the final product based on the selected colour tone. For dyeing of textile substrates, the natural dyes of turmeric, red cabbage and oak gall with the combination of ferrous sulphate were used. The dyes were extracted in the water medium. These extracts were used as a dyebath. Half of the silk and wool fabrics were mordanted with the aluminium sulphate. To determine the effect of the dyebath dilution on the dyeability of fabric substrates, the dyebaths were diluted with distilled water in the following ratios: 1 : 0; 1 : 1; 1 : 2; 1 : 5 and 1 : 10. To ensure uniform dyeing, the fabrics were dyed using the exhaust dyeing process in the Launder-o-meter laboratory apparatus. Dyeing with the turmeric and red cabbage dyes was performed at liquor to goods ratio 40 : 1, at 60 °C, for 60 minutes. Dyeing with the oak gall dye was performed at liquor to goods ratio 40 : 1, at room temperature, for 20 minutes. The mordanted and non-mordanted samples were numerically evaluated for their colour, using the Datacolor Spectraflash 600 Plus-CT spectrophotometer and the CIE L*a*b* colour system. The colour measurements were carried out after the washing fastness test as well. The results show that the dyebath dilution affects the substrates dyeability, as it made the samples brighter (CIE L* values are raising). Moreover, the results show that the dyebath dilution affects the CIE a* and CIE b* colour values as well. Dyeing silk with the oak gall dye, the dyebath dilution lowers the CIE a* and CIE b* colour coordinates; the more the dyebath was diluted, the greener and bluer the samples were. On the other hand, there was no constant lowering or raising of CIE a* and CIE b* values with the wool samples. Diluting the red cabbage dyebath raises the CIE a* values and lowers the CIE b* values irrespective of the substrate or mordanting, as the samples became greener and yellower. The dilution of the turmeric dyebath produces greener and bluer coloration of samples. The wool samples were redder and bluer compared to the silk samples. The effect of mordanting was also be observed, as the mordanted samples were darker than the non-mordanted ones. It was established that the turmeric dye and the red cabbage dye have poor colourfastness to washing.