Hue / Saturation option will let you change the Hue, Saturation and Lightness values of the design.
Go To Colors >> Image Color Adjustments >> Hue/Saturation
Check the primary color only option. Changes in Hue, Saturation and Lightness will be reflected only in the area of selected primary color
Random Variation if enabled, will automatically apply random Hue, Saturation and Lightness values to the design. The variation can be changed using the slider control of Variation.
Check on primary color and enable Random Variation will apply the random Hue, Saturation and Lightness effect to the area of selected Primary color only in the design