SunFounder ESP32 Manual page 494

SunFounder ESP32 Starter Kit
2. Make RGB LEDs light up in the appropriate color
Before understanding the code, we need to understand the RGB color model.
The RGB color model is an additive color model in which red, green, and blue light are added together in various ways
to reproduce a broad array of colors.
Additive color mixing: adding red to green yields yellow; adding green to blue yields cyan; adding blue to red yields
magenta; adding all three primary colors together yields white.
488 Chapter 4. Play with Scratch