The cells of the first table are supposed to have an aqua background. The background of the cells in the second table is supposed to be filled with diagonal gradient with a tick at the top left corner. The background of the cells in the third table is supposed to be filled with diagonal gradient with a tick at the bottom right corner.
Reference images may be found at http://test.csswg.org/suites/css2.1/20110323/html4/table-backgrounds-bs-colgroup-001-ref.htm.
IE8 Mode, IE9 Mode, IE10 Mode, and IE11 Mode (All Versions)
The gradients in the second and third table do not match the reference images.
The test fails because positioning of the background is not based on the table element but the colgroup element itself.