The cutoff for grey quests seems to be wrong on a lot of them, at least for the low-level quests, I don't know if the cutoff is higher for high-level quests. It should be "quest level + 5", but is shown as +6 in their descriptions. For instance, The New Horde (ID 787) turns grey once you hit level 6, but it's marked as [7] in its description.

Sorry for the late response on this. I did some investigation and yes, the range of green quests changes with your level. For example on level 9 it is questLevel +5, but on 50 it is questLevel + 10.

I updated our code to use the correct values Blizzard uses as well.

This should be fixed with ea52634

If you still have issues please report back.