From the early to mid-1960s Riley worked
exclusively in black and white, gaining critical attention internationally for her Op art paintings, before shifting her
palette to
grey and then to colour in 1967.
In addition to the intentionally restricted red, blue, and yellow
palette — relieved by black, white, and a
grey mixed from the other pigments — Redstone's formal vocabulary encompasses rectilinear shapes and grids aligned
exclusively along 45 and 90 degree axes.