Blue Lums are the source of life in the universe. Blue Lums grant newly born creatures their first breath, and creatures carry their Blue Lums with them for the rest of their life.
The Blue Lums have a very close resemblance to Neri, who is from The Legend of Zelda: Phantom Hourglass. Neri's wings are blue, while the Blue Lum has clear wings.
Rayman can find Blue Lums underwater and touch them for an extra breath of air.
Rayman 3: Hoodlum Havoc GBA and Rayman Raving Rabbids GBA
In the GBA version of Rayman 3 and Rayman Raving Rabbids, Blue Lums allows Rayman to use his Super Helicopter in certain places. They are also found in unexpected places sometimes.
In this game, Blue Lums are used to stay in the Super Helicopter for a longer time.
Rayman 2: The Great Escape PC
In the Rayman 2 PC Version, there are three blue lums in the game that give you unlimited oxygen. Two out of three of them are in the first level of the Fairy Glade. The last one is in the last level on Whale Bay.
On Rayman Revolution, several streams of bubbles are used instead of blue lums.