I had intended for the wings to have a lining of red, but I must have made a mistake and picked the microbe that developed a yellow appearance because it also appeared yellow in my TSA plate.
As you can see, I chose the MAC plate to display my art. The MAC plate is a differential and selective medium that selects against gram positive bacteria. For that reason I chose all gram negative microbes. MAC contains a pH dependent red dye and lactose and peptone as carbon sources. Microbes that feed on the lactose and produce acidic lactose would change the agar to pink, and microbes that feed on peptone convert it to ammonia; this is why my MAC plate turned a lighter yellow color.