Enemy Discoloring

Enemy Discoloring is an intentional quirk of the Personalisation A.I., closely related to the concept of Dynamic Level Rearrangement. It's the name given to when regular enemies in the game have their colours, and sometimes behaviours, altered. These discolourations are usually consistent with their behaviours between copies, and can either prove a lesser or greater challenge for the player.

Aesthetic
Aesthetic discolourations are usually the result of enemies ending up in levels that they don't usually belong, working in tandem with Dynamic Level Rearrangement. For instance, if a Goomba were to spawn in Hazy Maze Cave they would appear blue. This is in reference to how Goombas appear blue in underground levels in the original Super Mario Bros..

Behavioural
Behavioural discolourations not only change the colour of an enemy but alter the way that they move or interact with the player. These changes are typically minor, although there are a few examples such as Red Koopas that change the enemy in a substantial way.

Theorising
The existence of discoloured enemies is entirely based off the rhetoric of players, although many of these players regard the same attributes of these discoloured enemies. Some of the enemies referred to, specifically the Chill Bully and Red Koopa Troopa, appear as unused assets in both Super Mario 64 and Super Mario 64 DS respectively. The appearance of the Red Koopa in Super Mario 64 DS, which is already speculated to be based on a very personalised version of Super Mario 64, might be based off an instance of enemy discolouration.

Some people consider the White-eyed Chomp an example of enemy discolouring. This is due to how similar it is to the idea of changing the colours of enemies, and also because the White-eyed Chomp can sometimes exhibit differing behaviour from its original counterpart. This includes the Chain Chomp wandering aimlessly from its pole. The lack of pupils could be inferring that the Chain Chomp is blind, and therefore blindly running around.