Actually the breeder who you are buying your female from have done quite a few hypo pastel X colored breedings to produce hypomelanistic hets in the past. If you look at page two of their pictures they show a few hypo crosses.
I personally would breed out to the colored, and produce hets, and if your goal is to eventually produce hypomelanistic babies cross a pair of hets or a hypo pastel X hypo het. A lot of the Hypo Pastels are related to some degree so crossing them out to another line before you yourself breed them back into a hypo pastel line would add some different genes/characteristics, and I believe lessen the likely hood of problems in the offspring to some degree. Another plus other then the new genes would be the color increase you would get in your hypomelanistic offspring when you breed the hets.
This season I'll be crossing two of my hypomelanistic dragons out to very high colored orange/red dragons from different lines. My goal is to cross the hets from these breedings, and produce hypomelanistic with the increased orange/red coloration. It has been done before, but I feel the size, health, and color of the dragons I'll be crossing my hypos to will only benefit, and add size, vigor, and nice high colors to the hypomelanistic offspring I will eventually produce by crossing the offspring.
Good Luck with your new dragon, and good luck in your future breeding whichever way you go about doing it.
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