An example sheet of DLT barcodes showing colour-coding. The standard allows six letters or digits and we can fit 18 labels per sheet. The top half of each label is folded behind it to make the label lock in the label slot, so adhesives aren't required.
If you don't want to get your hands dirty, you can use my DLT label generator which will make any labels you like. It's free! (but not converted to this new page yet!)
If you use AMANDA and don't have a tape library, you might also be interested in my custom Postscript inlay for DLT cartridges for DLT cartridge cases.