Mixing the two colors of red and yellow together creates orange, which is a hue in between the two colors. The color red is approximately 650 nanometers (nm), while yellow is 570 nm. Orange's wavelength ranges from 585 to 620 nm. An nm is one billionth of a meter.
Mixing together red and blue creates violet, which lies in the middle of the two. Blue light is approximately 475 nm, while violet light is shorter and more scattered at 400 nm. To create indigo, you also mix together red and blue but instead of mixing equal parts of each, you mix two parts blue to one part red.
Mixing together both blue and yellow creates green, which is the third and final secondary color. Green light measures approximately 510 nm. Plants, including grass, are green because plants absorb the rest of the colors and reflect green.
Make the secondary or primary colors darker by adding black, which is not considered an actual color or lighter by adding white, which is also considered a hue. Examples include pink, which is created when mixing red and white together or maroon, which is a combination of red and black.