cformat switch: b
Allows you to apply custom background colors to individual rows. This is the same concept as cformat c except that it only uses colors defined by RGBbg clauses (either on the pseudo column or on any other column). The column must contain a single character matching an RGB Color Index.
Note that as with with other column types used to encode row attributes (see cformat b, c, C, f, @), rather than row data, you almost certainly want to pair this with the cformat code H to hide the column.