Are you receiving other (rare) dyes?
If not, you may need to increase the ilvl of your retainer.
If you ARE getting other dyes, just not the color you want, then it's just RNG and there's really not much else you can do about it.
Rare dyes are now available for trading in choco feathers, if you have some extra laying around and/or don't want a Twintania mount. I think they might also be available in the Cash Shop if you don't mind to spend a few bucks...?
