Gray - You cannot increase your skill by making these items or harvesting these items.
Green - These items give you a fairly poor chance to increase your skill. You can still do it, but its going to take a lot of gathering/creation to up your skill with these items.
Yellow - These items give you a reduced chance of increasing your skill. It's still pretty reasonable to try to increase your skills with these items.
Orange - These items give you your best chance of increasing your skill. For many of the Professions, making an orange item will always increase your skill.
Red - Your skill is not high enough.
He should be able to level it up all the time till a certain level, most of the items he can make is orange.
