Like many loot-heavy games, Borderlands 2 uses colors to distinguish the rarity of the items spread across its wasteland. That color shines out from loot in a beam, and it features on their descriptions in the title. For colorblind players, distinguishing those different colors from one another is problematic, so Gearbox is modifying them to make them more identifiable, as well as denoting the color in text on the descriptions.
It's a shame it wasn't there when the game shipped - it it had, Gearbox would've been able to apply i to just one side of a split-screen, rather than the whole screen. Still, it's good it is being added, and that Gearbox has gone to the lengths of letting players specify different types of colorblindness; when toggling the mode, players can select Deuteranopia, Prtoanopia, or Tritanopia.