I've noticed this too, green or not the triple xp bonus is based off the difference between the highest lvl toon and the quests level. If a RAF toon is 5 or more levels above the quest then nobody gets the bonus.
Even with multiboxer assisting with quest turnins one toon gets the quest in a split second faster than the rest so I've had instances where one toon dings and the rest don't get the bonus and fall behind. Useful to have an addon that shows quest levels, I use Lightheaded.

Also I posted about this in the Customer Service forum and the Bug forum and either nobody cared or nobody noticed