Mr. Hilleary produced works that embodied the most salient aspects of the Washington Color School of painting, although he said he developed his style independently and did not consider himself a member of the group as it was most strictly defined, according to his son.
The school — whose most prominent artists included Kenneth Noland and Morris Louis — flourished in the 1960s. With clean lines, precise shapes and vibrant hues, it offered an alternative to the seemingly unruly abstract expressionism that had dominated the art work in previous decades.
Mr. Hilleary, who trained as an architect, embraced color painting’s geometric purity. He was able to “distill lyricism out of pure line and color,” Washington Post arts writer Michael O’Sullivan once noted.
“The ‘Striae’ paintings,” O’Sullivan wrote, “all of which feature strands of vertical color that alternately clump together and separate, forming a forest-like energy field, have a brooding electricity. They almost