Orange-texted items

Are all of them quest items?

Gold items (with goldy yellowy orange colored text) are all quest items or important items that you can't sell yes. DO NOT DROP THEM!!! Find a permanent storage shelf if you need to put them down.

Blue colored ones are enchanted items.

DO NOT DROP THEM!!! Find a permanent storage shelf if you need to put them down.

Well, that's not necessary. If you've completed every single quest in a particular expansion, they're not needed anymore (except for the three belts in HOLIII). If you keep them, it just slows down the save/load functions and even causes random BUGS!!! (not quite sure about the 2nd...)
Keep some fine blades and cloths with you and trash all this unsellable rubbish in a huge forest full of robbers if your active quest log is clear .

Well yes but I was referring to don't put them down whilst you are still on that expansion