Colman was chief of diagnostic pathology and clinical medicine for Continuum Health Partners, including St. Luke's-Roosevelt Hospital Center and Beth Israel Hospital. He was also a professor and vice chairman of pathology at Columbia University's College of Physicians and Surgeons. Prior to working at St. Luke's-Roosevelt, he was the head of the Center for Clinical Laboratories at Mount Sinai Hospital. Colman is credited with ground-breaking research on folate. During his doctoral research at the University of Witwatersrand, he discovered that the anemia suffered in many rural communities under attack from apartheid was caused by a folate deficiency. His research eventually led to the fortification of food products with folic acid, which is endorsed by the World Health Organization and the United States Food and Drug Administration. For much of his medical career, he worked closely with Victor Herbert on folate research. He also developed a technique for delivering supplementary vitamin B-12 with a nasal gel to those with Crohn's disease. Colman also worked extensively in the area of DNA research, calling for increased standards in its use as a forensic tool. Throughout the 1980s, he collaborated with attorney Peter Neufeld on work about the proper use of new scientific techniques in criminal cases. Colman frequently provided expert testimony in criminal cases on the veracity of DNA fingerprinting and quality control in criminology laboratories. Colman and Neufeld identified a problem with the lax regulation of crime laboratories, noting "there is more regulation of clinical laboratories that determine whether one has mononucleosis than there is of forensic laboratories able to produce DNA test results that can help send a person to the electric chair." In 1990, Colman and Neufeld summed up this work in an article in Scientific American, which was reprinted in numerous textbooks. The National Research Council of the National Academy of Sciences released their own policy on rigor and oversight in forensic science two years later.
In 1987, Colman founded the West Side Soccer League. He was the league's regional commissioner from 1987-1996. He went on to become New York area director of the American Youth Soccer Organization. According to one source, Colman grew up playing soccer in South Africa and worked to educate American parents who had no soccer experience about the game. In 2005, after Colman's death, a sports field in Riverside Park was named Neville Colman Field in honor of his contributions to youth soccer in New York City.
Death
Colman died in 2003 in New York City. The cause of death was metastasized gastric cancer.