Although Silver Lums are never mentioned in the original Rayman game, it is possible that the silver light Betilla shoots into Rayman's symbol is a Silver Lum as they serve exactly the same function, are given, received and absorbed in the same way, look similar, and are also created by a fairy, like in Rayman 2.
In Rayman 2
—Manual, Rayman 2
The Silver Lums which appear in Rayman 2 have all been created by Ly the Fairy, who must gather energy in order to do so. She says that combining the energy has become very difficult due to the destruction of the Heart of the World, which is why she cannot restore all of Rayman's powers as he had hoped. Rayman absorbs Silver Lums through the symbol on his chest, which then shines brightly. Once absorbed, they endow him with new powers, or upgrade powers which he already has. Unlike most Lums, they lack eyes and wings, appearing as simple orbs of light.
Look for them, they provide extra life!—Manual, Rayman 3 (Game Boy Advance)
In the Game Boy Advance version of Rayman 3, Silver Lums are much more common and hold far less significance. Here they do not grant Rayman powers; instead they grant him an extra life for every one he collects. They are found throughout the game rather than being granted by Ly; instead Ly gives Rayman new powers by shooting large, fiery orbs of light into him. These orbs are much more similar in both function and effect to Silver Lums than the actual ‘Silver Lums’ which appear in this game.