Really stupid question here, but I don’t understand why the mask below isn’t colored blue?
Tom
I think the reason is that not the mask is shown in the images but the geometry. Open the Layer Manager. There you can change the visibility for masks vector data (geometries), bands.
Yes, it looks like the Mask Manager controls the color displayed in the Navigation window, while the Layer Editor inside the Layer Manager controls the Mask color displayed in an Image panel.
I’d submit that it would be a Good Thing to make those two do the same thing 
Thanks!
The Layer Manager controls what is shown in the Image View. For bands, masks and vector data and other layers.
The Layer Editor within the Layer Manager currently has only generic image layer properties and none special for masks. This is missing.
The Mask Manager changes the style and visibility only for masks.
The only difference between Image View and Navigation View is that in the Navigation View the vector data elements are not rendered. And here you are right, they should also be displayed.