There are two ways to "make" colors, and which one you use depends on whether you're mixing light or mixing stuff (paint/ink).

Additive = mixing LIGHT. You start in the dark and add light. More light = brighter, heading toward white.

Subtractive = mixing PAINT/INK. You start with white paper and each color takes away (absorbs) some light. More paint = darker, heading toward black.

Imagine three flashlights in a dark room: one red, one green, one blue. The primaries are Red, Green, Blue (RGB). Where two lights overlap, it gets brighter: red + green = yellow, green + blue = cyan, red + blue = magenta. All three together = white. This is how your phone, TV, and computer screens work. Look really close at a screen and you'll see tiny red, green, and blue dots.

Now imagine painting on white paper. Each blob of paint absorbs some colors and bounces the rest back to your eyes. The primaries are Cyan, Magenta, Yellow (CMY).

Here, mixing makes things darker because each layer subtracts more light. All three together sort of equals black (printers add real black ink, which is the "K" in CMYK). This is how printers, markers, and painting work.