Pellets I never had much success with in feeding my dragons. I feel it is best to feed variety of foods, greens and insects. Some pellets added to fresh food on a regular basis is fine. Moistened is always best as it provides far more hydration to your dragon. Soak in water before adding to top of salads etc.
As for the mouth coloration, I don't think there is anything wrong...though lack of color in gums etc could indicate various things. Very red or signs of inflammation I would think bacterial infections (ie mouth rot). If yellowish it may be sign of kidney or liver failure. Having a vet examination, especially with one very familiar with reptiles and bearded dragons is always good, if you are worried. Slight variations between dragons is probably normal though.
If he's eating well, active, alert and behaves perfectly normal for a healthy happy dragon, then the slight difference in color is probably nothing to worry about. Watch weight, how much he eats and how often he poops, if these change or the color of his mouth gets even paler or darker purple, I suggest a vet visit.
-----
PHLdyPayne