Not sure if this is possible by default in Silhouette, don’t think it is but correct me if I’m wrong. But this should be fairly simple to knock up right as a tool?
Make a layer the colour blue for example and then select the layer, run the tool, and all the roto shapes inside that layer would also change colour in the viewer to blue. (or whatever colour you set).
Or perhaps for lots of layers, select the amount of layers you want, run the tool and select the colour you want all the splines inside to be through the tool…
It’s been requested a few times to me but not had any time to look into it further. What do you think?