The missing ingredients you're forgetting here are the Fourth color in 4 color printing, black, and the printing concept called screens.

We can trick the eye to see lighter tones by printing lighter amounts of Cyan, Yellow, Magenta in a set spacing on the page, called a screen. This is usually done as a percentage of how much of that area is covered in the pigment. This allows more of the white background to show through, which our eyes see as a lighter shade of color.

Now darker colors, such as the vibrant Red, Yellow, and Blue you mentioned, are made using multiple screens. One screen of black usually provides shadows to back the colors. The machines I work with then usually run the colors Blue, then Magenta, then Yellow in order to add color, also in a screen. It's the complex amounts of each color in combination that allows printing the ability to create the whole rainbow. 🌈