Not true in the slightest...
Red, Yellow and Blue are the primary colors in color theory.
They're the colors that can't be created by mixing any other
colors on a palette. RYB being taught as primary colors isn't
some attempt by elementary schools at dumbing down fact
so their students can grasp the concepts more easily.
CMY (and Black) are the primary colors used in color printing,
not art. No painter has ever mixed CMY (and Black) on their
palette. Magenta wasn't even created until the late 1800s.
Cyan isn't even a single color; it encompasses blues and
So as far as art theory goes, Red Yellow and Blue are the
The article goes on to say that many painters also now use the CMY color model as well. For those who don't they keep many colors on their palette that cannot be formed by RYB.
During the 18th century, as theorists became aware of Isaac Newton’s scientific experiments with light and prisms, red, yellow, and blue became the canonical primary colors—supposedly the fundamental sensory qualities that are blended in the perception of all physical colors and equally in the physical mixture of pigments or dyes. This theory became dogma, despite abundant evidence that red, yellow, and blue primaries cannot mix all other colors, and has survived in color theory to the present day.
Using red, yellow, and blue as primaries yields a relatively small gamut, in which, among other problems, colorful greens, cyans, and magentas are impossible to mix, because red, yellow, and blue are not well-spaced around a perceptually uniform color wheel. For this reason, modern three- or four-color printing processes, as well as color photography, use cyan, yellow, and magenta as primaries instead.