The CSS border-color property is shorthand CSS to specify a border color for all sides of an HTML element. Specify one color value to make all borders the same colors. Specify two color values to make right-left and top-bottom different colors. Specify four color values to independently color each side. The other CSS shorthand properties work in a similar way allowing you to target particular sides if needed.
Simple Color Name
red, green, blue, etc...
RGB Color Value
rgb(0,0,255), rgb(0,255,0), rgb(255,0,0), etc...
Hexidecimal Color Value
#FF0, #009900, #0099FF, etc...