Born in Cologne, Germany, Aach studied painting as a young boy with expressionist artist, Ludwig Meidner (1884-1966) as a mentor and for whom he served as an atelier boy, until Nazi persecution forced him and his family to flee to New York, where he arrived in 1938 at the age of 15 years old. After enlisting in the U.S. Army in 1942, becoming a U.S. citizen in 1943 and being sent back to Europe to serve in the Military Government in Kassel, Germany, Aach returned to New York in 1946 where he resumed his art studies at the Brooklyn Museum Art School with fellow artists John Ferren and Rufino Tamayo. In 1948, he moved to Mexico for two years to further study art at the Escuela de Pintura y Escultura in Mexico City. It was in that period that Aach – partly influenced by John Ferren – acquired a strong preoccupation with color that shaped his career.
Between 1954 and 1963, Aach experimented and consolidated his philosophy about color, developing a style he called color expressionism. All the while, Aach worked at the Art Crayon Company formulating paints and gaining access to otherwise unobtainable pigments. He made his own paints, packing them with pigment, and by the mid-1960s, he turned fluorescent pigments. In 1965, Aach began teaching studio courses and color theory at Queens College in New York. Seeking a purer framework to explore color relationships, Aach abandoned the sensuous brushstrokes of his earlier paintings and, instead, began working with larger regions of color.
Aach published a leading book entitled Goethe's Color Theory in 1971 and two major series of paintings entitled “Procession of the equinoxes” and “Split Infinity” in 1974 based on his color theory. As the 1970s progressed, Aach increasingly travelled back to East Germany, giving him the opportunity to study at the Goethe archives in Weimar. In 1979 Aach was diagnosed with cancer. Though weakened by the disease, he maintained his painting practices and when that became too difficult, he continued to draw. Herb Aach passed away in 1985.