Just to point out, the 4 original types of Lums were there before Polokus was created.
One day, the Lums focused themselves into thought, and their consciousness brought to life a strange and marvellous creature, Polokus. His power is such that his smallest dream or desire becomes reality.
Apparently, many types of creatures were alive before the existance of Polokus, which explains why some creatures don't bubblize but just die:
Blue Lums contain the first breath. They are the origin of all life. Each creature receives at birth his Blue Lums and keeps them until the day they die.
But this is pretty interesting, take a look!
Polokus decided to use his powers to bring people to the world. He began with the magical beings, and dreamed up the fairies. They are his emissaries. After the first 4 Lums, they made the Silver Lums which give you your special powers.
There's the possibility that the fairies had times to increase the number of Lums, or even create a new species.What if the Lums in RO are the sixth type of Lum? With their happiness and energy, they provide illumination to the Glade. They not only come in yellow, they can change their colour to red, or even purple.
Today I took the time to check the Knowledge of the World, nothing is contradicted, just difficult to explain.