Something to this effect should be possible. Even though we tint items based on level and class, its not completely the same thing. Level and class are known values, so checking items against that data is very fast. In order to find out if an item is needed for a collection we have to go through every collection to see if the items is required, and then check to see if you have it or not. CPU-wise its more time consuming.
Implementing this is easy, the big question is whether or not it creates a perceivable delay. My guess is probably not long enough to matter.
We already tint recipe scrolls grey if they've already been scribed, so would it make more sense to tint collection items grey if you don't need them anymore and just leave the ones that you do need in white?
LINK
(Rothgar) Re:(( Proposal: "Need-It" (tm) Green silhouette for Collectables.
