Yellow and purple are complementary colors on the color wheel, meaning that they are opposite each other. When these two colors are mixed, they can create a neutral or grayish tone, which is often used in hair color to cancel out unwanted tones.

In hair coloring, yellow tones often appear when hair is bleached or lightened, while purple tones are commonly used to neutralize unwanted brassy or orange tones. Yellow and purple can be mixed together to create a neutral or grayish tone, which can be useful in toning or correcting unwanted tones in hair.
When yellow and purple are mixed in hair coloring, the resulting color will depend on the specific shades and formulas used. If the yellow and purple colors are mixed in equal parts, the resulting color will likely be a grayish or neutral tone. However, if one color is used in greater amounts than the other, the resulting color may lean more towards the dominant color.
It is important to note that the final result of mixing yellow and purple in hair coloring may also depend on the starting color of the hair. For example, if the hair is very light or bleached, the resulting color may be more gray or neutral, while if the hair is darker, the resulting color may have more depth and dimension.
Overall, yellow and purple can be mixed together in hair coloring to create a neutral or grayish tone that can help to cancel out unwanted tones in the hair. However, the final result will depend on the specific shades and formulas used, as well as the starting color of the hair. It is always best to consult with a professional hair colorist for personalized advice and recommendations on achieving the desired hair color result.