It is my understanding that if you take a standard grey with no leu in the lineage and take a Leu you have a 50 percent chance of producing a leu.
To produce a Leu - BOTH parents must carry the recessive gene for the leucistic coloring and pass that gene on to the offspring.
Breeding a standard grey with a Leucistic glider would produce ONLY grey gliders that are 100% leu Het. All joeys would carry 1 copy of the recessive gene from the leucistic parent.
The Het stands for heterozygos meaning the glider carries 1 recessive gene for the trait - which it can pass on to its off spring.
Breeding two UNRELATED grey gliders that are both 100% leu het will produce a Leucistic joey 25% of the time. The other joeys would be standard grey and be identified as 50% Leu het because they may or may not carry the recessive gene.
There are only 3 initial leucistic glider lines. It is always best to check lineage when breeding any glider with leucistic genes to ensure the pair are not related any closer than 3 generations back in their ancestry. There is always a chance that two leucistic gliders will be related more closely and should not be paired for breeding.