CSS supports 140+ color names, HEX values, RGB values, RGBA values, HSL values, HSLA values, and opacity.
RGBA color values are an extension of RGB color values with an alpha channel - which specifies the opacity for a color.
An RGBA color value is specified with: rgba(red, green, blue, alpha). The alpha parameter is a number between 0.0 (fully transparent) and 1.0 (fully opaque).
The following example defines different RGBA colors: