Compare the Old and the New color wheel.

The oppositions on this color wheel only make hues of brown, Instead of making neutral dark grays and blacks.

The color wheel is taught to most people today (School Standards for all States except N.Y.) is this twelve hue color circle as developed by, Tobios Mayer in 1775, Otto Runge in 1809, Chevreul in 1839, and Johannes Itten. 
 

Chevreul, 1839, Chevreul made a twelve color wheel, Yellow, Red, and Blue again, wrong complements, wrong after images, Yellow is not opposite purple, Ultramarine Blue is not opposite Orange and Red is not the complement of Green. His complements in "Simultaneous Contrast of Color" made mud, he never completed his solid model.

Albert Munsell, 1905. He made a five color wheel with no triad. The principle colors he did have were, red, yellow, green, blue, and purple. No Magenta or cyan. In a 5, 8 or 10 color wheel there is no triad possible. Next he darkened the colors with Black, mixed them with Gray, and tinted them with White, and numbered them all. This is still taught today. An eight or five or ten color wheel will not work. It has to be a 3, 6, 12, 24 or 36 color wheel to have a triad and correct opposite secondaries. In my element color wheel, colors do not darken with black like the RGB color wheel and the Munsell color wheel.

1916, The last color wheel (square) of college record was by Church-Ostwald. It has Yellow, Red, Sea Green and Ult. Blue at the corners. It made way for the new coal-tar colors, all pigments were replaced by there top-tone matching colors. Naples Yellow, Rubins favorite, artist's favorite for two thousand years, was replaced by a mixture of Zinc and Ocher. Pigments were moving from the Iron Age to the Oil Age. Ostwald had no regard for opacity, or raw pigment content or the paints handling qualities. Only the final dried chip color counted. 

This represents the Red Yellow Blue (RYB) color and painting theory that is still accepted today. 

Actually it doesn't work any better than the ROYGBIV color theory that was popular when I went to school. 

Young artists are having trouble, they are being taught a color system that doesn't work.

On the Red Yellow Blue color wheel a Red tomato would use Green and darken the Red to Brown. Now that's ugly.

None of the oppositions on this color wheel will mix into any color but a medium brown because:

The oppositions on this color wheel make neutral dark grays and blacks, not just browns.

This color wheel matches the RGB, CMYK, YMC full chroma colorwheels plus natural crystal colors, oxides, Chemical Class colors, vegetable colors and the rainbow.

This color wheel matches the  RGB, CMYK and YMC color wheel divisions of colors, but not in the way their colors get dark. The natural painting artist needs the correct dark color ranges. 

This is a crystal color wheel. Original and toward color theory. Don Jusko, 2000.

Each color opposition on the RCW mixes into a dark neutral that tints a neutral gray. Giving you a complete range from bright color to the deepest shadow of that color.

The Old RYB colorwheel has a Red/Green opposition that should be Magenta/Green instead. On that Red, Yellow and Blue color wheel, a red tomato would use green to make a shadow on the tomato, making Brown. Ugg..

No wonder today's young artists are having trouble, they are being taught a system that doesn't work. So were you I daresay. On the RCW color wheel a Red tomato would use Cyan to darken the Red into natural shadow color. 

Only on this real color wheel are yellow and brown in the same color column path.

Only on this Real Color Wheel are cyan and ultramarine blue in the same color path.

Only on this Real Color Wheel do all color oppositions darken each other to neutral correctly.