I also have a Text & Image visualisation set up with the same formula so when a colour is selected, it shows up there. However, when I select 'Dark Colours' it does not show up there, but Red and Blue do.
Does anyone know what I'm doing wrong for 'Dark Colours' to not appear in the text box? I'm guessing it's because more than one colour is selected (both Grey and Black). Does anyone know how to get around this?