Suggestion (Required)

When I play, I often have 1 golden bag of holding for quick access tools (which I call Ryobi or Rigid because those are power tool brands), and then one for a dump pouch to pick up loot while adventuring. The dump pouch is one of many that live in my ender chest, as well as a few other bags that live in my ender chest. All those bags look the same, so it would be nice to have a visual indicator of things that are assigned. I use Shulker Box Tooltip to show the inventory on a mouseover, and it works with your bags too.

Shulker boxes can be dyed, and before I installed Bags of Holding, I used a lime green shulker box (named Ryobi) as my tools chest, and a natural colored one as a sort of dump pouch. I also have several color coded shulker boxes in my ender chest so that I know what's in them based on my color scheme.

Leather can be dyed in minecraft, and we now have a color customization infrastructure with the various armor trims. Either or both systems could be applied to the bags of holding, depending on your preference.

For another example, Reinforced Shulker Boxes wind up with a two tone color based on what color they are dyed and what kind of shulker box they are. I think that might be a good idea for the bags of holding too; an accent color instead of a full color change.