That's true. In order to get a blizzard you need to breed 2 geckos that each have 1 or 2 copies of the blizzard gene. Very often, though, geckos with one blizzard gene copy come out more speckled than the average gecko. You could breed the offspring (assuming that one of the parents is a blizzard) back to the blizzard parent to get blizzards in the next generation.
Aliza