I label the box.
I never put untried juices in cartomizers. A manual KR808D-1 can use a drip tip with a standard resistance DSE901 atomizer (auto battery should use cartridges with it but if you can mange to cut blue foam stuffing for the cart that would let you remove, rinse and pat dry the foam). I use a manual battery, atomizer and drip tip to test juices, trying them from weak/sweet to strong to clingy and blowing out the atomizer between them.
Labeling filled cartos - you can use the colored end caps from SmokelessImage, or vinyl map dots, or or a paint pen, or white tape and write on it. Some use colored combos of orthodontic colored rubber bands (Ebay) but I kept losing those inside my 510's PCC (down inside) so I stopped using them. I use colored drip tips from LiteCigUSA.net on a couple of carto colors. The only time I use a paint pen is to distinguish LR ones and to mark batteries so I know where the battery came from or if I have identical batteries I mark the best ones with a dot of gold.
Vapor4Life has colored cartos for KR808D-1. I use a few colors.