Hello,
I propose that, with possible conditions, users are able to color the box the item sits in and change it from the standard sky blue. Example shown below:
If data is a concern then can either make it local every time you play you set color or make it a monthly fee:

There could be one of two options for how to change the colour:
Option 1. Add Palette to withdrawal tab and user selects color when they withdraw the item, the items color box is now the color until put back into the bank, or otherwise used or deleted in some way, or put onto the MP. 
In our example the user selected the tier 10 club and wanted black. With black color box highlighted the user will remove the item from their vault in usual fashion via click and drag and the item will show with the changed color box in the inventory:

or when equipped

Again, the colour box is removed immediately if the item is put in a shrine/mute/glyph/etc or MP or put back into the Vault
Option 2: Add the Palette into the inventory and user can drag the item over the desired color for the color box:
Let me know what you think