How should i color my 20 shulker boxes in minecraft question for a friend who is at a loss?

Would be nice if someone answers his opinion

A specific color for each category.

Redstone things red, wood things brown, plants green, food pink, bone (flour) white, etc.

He can always have it with him, e.g. In the Enderchest. Then he knows directly from the color what is in which box.

And don't dye a few at all. He can then simply use it as a box replacement or dye it at some point if he needs more for a category.