Yellow is a primary color. It is also seen in the CMYK colors.
Yellow contains 50% red, 50% green, and 0% blue in RGB.
In CMYK, yellow contains 0% cyan, 0% magenta, 100% yellow, and 0% black.
Yellow is one of the safest web colors, listed as *FF0*, which is shorthand for its hex code (#FFFF00).
Here are some examples for using this color in CSS with Hex, RGB, HSL etc.