Serratia marcescens is an important pathogen of insects and in a recent study it was suggested that a genetically modified version of the organism could be used to control the mosquito responsible for carrying the malaria pathogen (1). A red pigment known as prodigiosin produced by Serratia makes it easy to trace during such experiments. Different strains of S. marcescens vary in the amounts of pigment they produce. The purpose of this project was to investigate the influences upon the pigmentation of Serratia marcescens, with the goal of finding a strain that produces maximum pigmentation. Such a strain would be useful as a biological tracer in future experiments. We tested five different strains of S. marcescens, ranging from producing no pigmentation to one giving a very deep red pigmentation. We have tested them on many different kinds of media including; Trypticase Soy agar, Nutrient agar, Brain Heart Infusion agar, Mueller Hinton agar, Deoxyribonuclease agar, Glucose minimal agar, Sabouraud Dextrose Agar, Pseudosel agar, Caprylate-Thallous agar, and Cetrimide agar with tyrosine. We also looked at potential influencing factors such as temperature and absence of oxygen. The results appear to show that certain conditions influence the pigmentation of Serratia marcescens. We have seen a change in the color and colonial morphology of S. marcescens in response to differing levels of oxygen. We have also seen the impact of temperature and growth media on the pigmentation.