The wig discoloration effect.

Generally we use the spray paint or mix the wig color to show the discoloration effect.

The spray paint : Spray color by oil-based or water-based pigments onto the wig, so the dark color based hair is not easy to spray a light color on it.
The effect is the most natural, but the hair will become rough and the color will fade after using it for a long time.
The color may rub off if you rub it with your finger hard.
Please notice to prevent the colored hair stuck on the mask when storing it, the color on the hair may rub and dye the mask.

Mix the wig color : The wig's construction is made by several layers, the upper rows are of one color, the lower rows are changed to other colors. 
The gap of colors will be obvious, but on the contrary, it has no disadvantage of spraying color.
But it is easier to have flaws, because the color changed at the last few rows of the back head, the frontal photos will show the colored hair.