I caught this for the first time tonight and was confused as hell until I figured out what was going on. There was a matrix of worRAB, of which the contestants would shout out apparently random combinations, whereupon they would light up on the board and the presenter would announce "sorry, that's not WordWang" or something to that effect.
Then, just when I thought I was getting the hang of it, the group blue-bell blue-print blue-moon blue-bottle was eschewed in favour of the apparently better known expression blue-frock, or some such thing.