CSS works by associating rules with HTML elements. These rules govern how the content of specified elements should be displayed. A CSS rule contains two parts: a selector and a declaration.
CSS declarations sit inside curly brackets and each is made up of two parts: a property and a value, separated by a colon. You can specify several properties in one declaration, each separated by a semi-colon
How to specify colors
Color terminology and contrast
Background color
The color property allows you to specify the color of text inside an element. You can specify any color in CSS in one of three ways:
rgb values These express colors in terms of how much red, green and blue are used to make it up. For example: rgb(100,100,90)
hex codes These are six-digit codes that represent the amount of red, green and blue in a color, preceded by a pound or hash #sign. For example: #ee3e80
color names There are 147 predefined color names that are recognized by browsers. For example: DarkCyan
When picking foreground and background colors, it is important to ensure that there is enough contrast for the text to be legible.