Mixing advanced gray colors involves blending various shades of gray to achieve a wide range of tones. To create these colors, you can start with a base gray and add different proportions of black and white. The process can be adjusted by incorporating various gray pigments or dyes. To create twelve distinct shades, experiment with the ratios and types of black and white pigments used, and consider using additional colors to modify the gray base. Techniques such as tinting, shading, and mixing complementary colors can also be employed to enhance the diversity of gray shades.