simple edit, but beyond me

[Darqwood]

I have a mod that will do something like what you're asking. You decide on several bag "categories" (Armor, Quest Items, Harvests, etc.) and assign a color to each of them. Then when you rename a bag with that category, the background changes to that color. This works across all your characters for inventory, bank, and house vault. The color change is permanent until you rename the bag again.

The color bag mod will appear with a configuration tab in the next DarqUI updater version, which will make it easier to set up custom names and colors. If you want to try the bags out before the update, the file is attached below. Category and color values are near the top of the XML script.