You couldn't change conditionally the color from fieldvalues within a listbox but you could use an expression-less straight-table (by disabling of suppressing NULL within the tab presentation) with your listbox field as dimension and using an appropriate coloring within the attribute-expression (click on the small plus-sign by the dimensions and you get access to font- and background-colors) like:
pick(match(YourField, 'qw', 'er', ...), red(), blue(), ...)
- Marcus
