The SNES console version of the game has a modified story in which the Princess has two hours to decide her fate (instead of 60 mins) and our hero has to conquer extra levels.
The original Apple II version, released in 1989 used only four colors. The MS-DOS version for the IBM PC as well as the Commodore Amiga and Atari ST versions released in 1990 used more colors allowing much more detail.
Later versions of the game (ie. version 1.3 and others) for MS-DOS featured different color palettes for different sections of the game and the ability to adjust the game settings for the computer used.
Certain versions released for home consoles (Super Nintendo etc.) remove some of the bloodshed.