RGBA color space
RGBA stands for the three colors red, green and blue and a number for the transparency of the color. The three color values can be specified from 0 to 255.
The value for the transparency is given by a decimal value from 0 to 1.
There are therefore 16,777,216 possible RGB colors, but they can be represented in countless transparencies as RGBA colors.
The RGB color system is one of the most common systems for web applications and image or photo editing. It is used in the creation and design of web pages and can be found in most image editing programs.