Color is not the factor for charming. Level is. And the range of color changes with your level, too. You may charm 80% of your level, if beastcraft is strong enough (look at manuals for Beastcraft on this host).
And your colorange is lvl/10+1. For example for a lvl20-Hunter, this would be 20/10+1=2+1=3. So
His MaxPet would be 80% of 20, which is 16. 16 would be blue for him, 17 would also be blue but he would'nt be able to charm. So just try some pets, some will and some won't, if they're too high.