Born in Oakland, CA, Humphrey received a BFA in printmaking and painting from the California College of Arts and Crafts, Oakland, and an MFA in printmaking from Stanford University, Palo Alto, CA. Since 1973, Humphrey has held various teaching positions, including at the University of California, San Francisco, University of South Pacific at Suva, Fiji, and University of Texas, San Antonio. She became a faculty member in the Department of Art at the University of Maryland, College Park, in 1989, where she teaches printmaking. Humphrey has also combined her skills as an author and illustrator for her children's book, The River That Gave Gifts. Her work has been shown in solo and group exhibitions in the United States and internationally. In 1996 she exhibited at the International Invitational World Printmaking Survey at the Museum of Modern Art, New York City, NY, and in 1999 she represented the United States at the Print Biennale in Ljubljana, Slovenia.

Humphrey is highly regarded as an artist and master printmaker. She created The Last Bar-B-Que after three years of studying many other famous renditions of The Last Supper, by artists ranging from Leonardo da Vinci to Emil Nolde. By adding chicken, bananas, papayas, watermelons, and mangoes to the menu of bread and wine, Humphrey shifts a traditional Christian theme to one that is contemporary and humorous, with an African American perspective. The vivid yellow, sienna, and blue allude to celebration and African influences. The blue color tone also represents divinity.