cformat switch: b
Allows you to apply custom background colors to individual rows. This is the same concept as the column type c except that it only uses colors defined by RGBfg clauses (either on the pseudo column or on any other column). The column must contain a single alphabetic character (A-Z) matching an RGB color index, or, if you prefer numbers, you can use a single digit 0-9 (which is treated as equivalent to A-J).