Blue Knuckles in Sonic the Hedgehog isn't a stand-alone game, but rather a reference to a potential ROM hack or fan-made modification of the Sonic the Hedgehog series for the Sega Genesis. In such hacks, Knuckles, usually Sonic's rival, might be recolored blue, altering his visual appearance within the game.  The "game" itself would be the original Sonic title with alterations to one character's sprite. Information about the specific creators of this modification would need to be further researched.

Blue Knuckles in Sonic the Hedgehog

Blockout (World)