After the latest update, items having damage and being located in my worn knapsack don't show the damage colours, despite them having damage.
I'm not entirely sure this is intended, however, given that lots of players store their items in a knapsack as well, it might be very useful to have those colours added to items stored in worn backpacks or knapsacks.
Added is one screenshot, showing the colours at items in the inventory and the missing ones at items in the knapsack
Thorin