The Retroverse is glitchy and full of errors.
Corruption is a breakdown of the code (digital, genetic, spiritual, etc) that creates a creature. It spreads like a disease, infecting life whenever one creature attacks another. Unlike most diseases though, it can be transferred at a range (including arrows and darts) and even through magic (with ranged or melee magic).
Sometimes you will encounter creatures that have a unique color pallet. This is an indication that they are different than your normal monster in some key ways. This is a very rare occurrence, having at best a 1 in 100 chance of happening. Here are some samples.
Blue: Intelligent and gentle. Blue variants shy away from violence but that does not make them good. They are far more likely to be peaceable towards other creatures and will sometimes offer help if requested. A blue variant gains the following traits: +2 to their Intelligence score. Can speak one additional language, even if they speak none. Resistance to psychic damage.
Purple: Confident and brash. Purple variants often take on an air of royalty around their kind and believe themselves to be superior to those around them. They will push others into the dirt, stepping on whomever they please to reach the top of whatever structure they are in. Purple variants gain the following traits: +2 to Wisdom. They are constantly in possession of double the gold their kind usually carries. Either their armor or one weapon they wield is magical or silvered.