The 37th BIENNIAL EXHIBITION OF CONTEMPORARY AMERICAN PAINTING: At the Corcoran through April 5; Tuesday through Sunday, 10 to 4:30; Thursday evenings until 9.

Joan Mitchell's giant canvases splashed with vibrant colors are the showstoppers of the Corcoran's 37th Biennial exhibition. Some of Mitchell's four-panel pieces, like the violet-purple-black-pink "la Vie en Rose," devour whole walls.

The show represents the personal tastes of curator Jane Livingston. "i think it makes for a better show, better quality and concentration, to have a singular, personal, limited focus," Livingston said. At the same time, she offers a caveat: "I want to go on record now to say I don't want to be elitist in perpetuity." A more extensive biennial is planned for February 1983.

This exhibit, a Corcoran tradition dating to 1907, is intended as "a simple follow-up" to the last biennial's display of deKooning, Kelly, Johns, Lichtenstein and Rauschenberg.

It offers a pleasing if not overly ambitious collection of works by post-modernist masters, all completed within the past few years. Sculptor Richard Serra uses black paint-stick on linen to create stark stripes that float near the ceiling and leave the viewer with a black feeling. (The catalog explains why this work is not contrived; something about conceptual pragatism . . .) Untitled works by Agnes Martin use delicate pastel horizontals at varying spaces to produce a ripple effect as the eye skips from line to line, reading the gradations of color.

Five pieces by Frank Stella, oil and epoxy on aluminum with wire mesh, speak of blatant artifice. Jutting from the walls, they suggest machine parts in purposely tacky colors and materials. And Richard Diebenkorn's subtle "Ocean Park" series of large abstract paintings depict geometric shapes and spaces.