I don't know if I'd look that far into it to be honest. It has a walnut neck, so just an easy way to differentiate which guitar is which.. and for Colin, which guitar for which song on the setlist. I'd like to think they would come up with a more imaginative name than Walnut haha
fun fact - I talked to Andy Hicks about Davey's guitar myself recently, and asked him the reason behind going for a walnut neck. Davey has/had another guitar (unsure if it was a strat, or something else random) that had a Walnut neck on it and he loved it. I wonder what that could have been. Maybe an acoustic??