Same product different design

Hi!

We sell the same product but only with different designs. How do we build this. We sell baby body items, customer can choose over 20 rompertjes  with a design, customer can select a rompertje with a pre made design, they can change there name or image on this rompertje. How do we manage stock like this? I have 1 rompertje for all the products. See attachment, you see a with rompertje and a pink rompertje this is the same product so have stock for 1 pink rompertje.