Star Discoloring

Star Discoloring, considered an equivalent anomaly to Coin Discoloring and Enemy Discoloring, and also generally associated with Dynamic Level Rearrangement, is a rarer anomaly that creates new types of Power Stars with new behaviors that typically scale from negative to positive and appear based on the player's skill at the game, with positive stars appearing more often to help people who aren't good at the game, and negative stars appearing to skilled players in order to add an extra challenge.

List of Documented Discolorations
''These are simply the most common behavior reported of these discolored stars and may be different from copy to copy. Some discolored stars are also unconfirmed, so it is wise to take them with a grain of salt. Finally, most of these stars have simply been reported to be recolors of regular Power Stars, though this page will only cover the manifestations of these stars that have unique mechanics.''

Green Stars
Green Stars are the most common instance of Star Discoloring and appear to have been reused in later Super Mario Bros. games by Nintendo, either by coincidence or due to them being inspired by this anomaly. Green Stars have been reported to appear in numbers of 1-3 in every main course, harder to find, and also considered "extra" collectibles. They would either contribute 2-3 stars to the overall star counter or have their own section of the game's HUD and unlock special levels, most commonly Challenge Courses.

Gray Stars
Often confused with Silver Stars manifesting in the original Super Mario 64, Gray Stars function in a similar manner to red coins and secrets, though they have an inconsistent overall total in a level, ranging from 3-12 Gray Stars being required to obtain a standard Power Star, or potentially other discolored stars. Gray Stars are also stationary, unlike Silver Stars.

Black Stars
Often confused with Power Ztars which are entirely different objects distinguishable by appearance, black stars take away from the star counter instead of adding to it and are much more common in levels than regular Power Stars. Some players have reported that stars do not go translucent as they normally do upon being collected but are instead replaced by Black Stars. To compensate for the inconvenience this would otherwise cause, they are often found near their counterpart's former location, and the original star usually respawns without having to reload the level.

Cyan Stars
Cyan Stars appear to be post-game stars found in every main course, and appear in groups of 1-3, similarly to Green Stars. Some reports state they can unlock new floors such as the 4th Floor, though most reports do not back this up and instead claim they are used to unlock the cannon in the Castle Grounds in order to talk to Yoshi or increase the Power Star account by 2-5. Coincidentally, ridable Yoshis have been reported to be more common in copies with Cyan Stars, especially when unlocked by talking to Yoshi on the rooftop.

Red Stars
Red Stars reportedly either increase the player's star count by 3-5 or increase the star counter by one. These stars are notable because they cause enemies and bosses to become more aggressive, gain more health and/or deal more damage, making the game much more difficult. They most often appear in Hard Mode, however may also appear outside of it if the A.I believes the player to be particularly experienced.

Rainbow Stars
Rainbow Stars, similarly to the Rainbow Cap, usually function as a power-up similar to the aforementioned anomalous cap or replace the Metal Cap. Alternatively, they have been reported to increase the player's star count by 5-15. In both manifestations, they are the rarest instance of Star Discoloring, often requiring intentionally performing poorly to make them appear. They are by far the most challenging discolored star to collect, as well, as, for example, the first report of Rainbow Stars said that the player had to use the cannon to shoot out into the void to attempt to hit it, and that it disappeared forever after they failed to obtain it.

Purple Stars
Purple Stars, also known as Dark Stars, are anomalous Power Stars seen in the unreleased Mario's Adventure game for the Special 64 that have been reported to appear in Super Mario 64. They usually appear in place of Power Stars obtained by defeating bosses, likely due to their connection to boss fights in Mario's Adventure. They usually only give 1 Power Star, though can give up to five Power Stars, with the difficulty of the boss fights scaling with the amount of Power Stars obtained by collecting a Dark Star.

Pink Stars
Pink Stars are notable examples of discolored stars because they appear to change size as they spin, which usually causes erratic behavior. However, this often time "freezes", meaning many who encounter them will see them just as larger Power Stars and perhaps a glitch. No special changes or unlocks have been reported from Pink Stars, meaning they may have just been an object test for the A.I. to see if it could manipulate object size. Strangely enough, some have even reported the star seen after clearing Bowser in the Sky to become a Pink Star. What this means is unclear.

Theorizing
Similarly to other "discoloring" anomalies, it is believed that Star Discoloring is an intentional mechanic of the Personalization A.I. used to change the game according to the player's needs to make it the correct difficulty for the player, either by increasing or decreasing the difficulty. However, it's rarity compared to the other anomalies of a similar nature is unexplained.

An alternative theory is that most of these stars were unused objects that were scrapped and either replaced with other objects such as the Metal Cap for the Rainbow Star or Red Coins for the Gray Stars, before being brought back by the Personalization A.I. in the form of a Power Star, explaining why several discolored stars appear to function like other objects instead of Power Stars.

Trivia

 * If one stays on the Super Mario 64 title screen where you can manipulate Mario's face long enough, two discolored Power Stars will appear: One white/silver, and one red. Oddly enough, they use the sprites from earlier builds of Super Mario 64 where Power Stars weren't fully modeled.