According to Wikipedia RYB aka artist’s primaries work by accident: “One reason the artist's primary colors work at all is due to the imperfect pigments being

According to Wikipedia RYB aka artist’s primaries work by accident: “One reason the artist's primary colors work at all is due to the imperfect pigments being used have sloped absorption curves, and change color with concentration. A pigment which is pure red at high concentrations can behave more like magenta at low concentrations. This allows it to make purples that would otherwise be impossible. Likewise, a blue that is ultramarine at high concentrations appears cyan at low concentrations, allowing it to be used to mix green. Chromium red pigments can appear orange, and then yellow, as the concentration is reduced. It is even possible to mix very low concentrations of the blue mentioned and the chromium red to get a greenish color. This works much better with oil colors than it does with watercolors and dyes. The old primaries depend on sloped absorption curves and pigment leakages to work, while newer scientifically derived ones depend solely on controlling the amount of absorption in certain parts of the spectrum. Another reason the correct primary colors were not used by early artists is they were not available as durable pigments. Modern methods in chemistry were needed to produce them.”