The three-digit hex form typically follows the RGB (RGB) format. Expanding this form to the six-digit form is as simple as doubling each digit:
The six-digit hex form typically follows the RRGGBB (RGB) format.
The eight-digit hex from typically follows the AARRGGBB (ARGB) format.
See https://stackoverflow.com/questions/29100161/convert-8-digit-hex-colors-to-rgba-colors for more informations.