I would have done a binEnum() to produce a state value, then use that state as the driving property in the Style Customizer. The style Customizer would also let you handle multiple properties, if needed.
binEnum({Root Container.Container.Image 137.Colour1},
{Root Container.Container.Image 137.Colour2},
{Root Container.Container.Image 137.Colour3},
{Root Container.Container.Image 137.Colour4},
) // Return position of first true value
Properties bound by the Style customizer will have the RGB venn icon.

