"Color is life, and light is the mother of color."
In 1924, Thomas began teaching art at Shaw Junior High School, a Black school in the then-segregated public schools of Washington, D.C., where she worked until her retirement in 1960. She dedicated most of her young life to teaching and promoting/developing youth arts programs. During the 1950s, her style evolved in several major shifts from figurative painting to cubism and then to abstract expressionism. As her art matured, Thomas began to embrace the bright colors that would later become her signature style. Thomas would not become a full-time, professional artist until she was 68 years old, when she retired from teaching.
Around this time, after completing her first art class at American, she began creating Color Field paintings, inspired by the work of the New York School and Abstract Expressionism. Thomas was the first African-American woman to have a solo exhibition at the Whitney Museum of American Art and, later in the same year, a much larger exhibition at the Corcoran Gallery of Art. Thomas denied labels placed upon her as an artist and would not accept any barriers inhibiting her creative process and art career, including her identity as a black woman.