Chicken Leg Tags

(Here is an old pic of my Girls)^

Hey I’m a first time poster here I have 11 Rock Island Hens/Plymouth Rock Chickens for egg laying only and wanted to name them all. 3-4 have distinct markings and I can tell them apart. But my parents can’t. I wanted to keep track of them to keep track of each bird’s health and wellness. We are new to the chicken thing and I don’t know what the little leg tags are called. If i can get different colored ones it would be nice.