It would be very helpful to have the option to assign unique colour to the different types of geometry in Rhino. That will also make selection of certain type much more convenient. For example:
Blend curves: Green
Projected curves, curve intersections, point intersections: Blue
Offset curves and surfaces: Cyan
Lines: White
Arcs, circles, fillets: Black
Fillet surfaces: Red
Blend surfaces: Orange
Extruded surfaces: Pink
History enabled (child) objects: Thicker outline
Of course, this is just an optional feature, so Rhino users who don’t like the idea simply won’t activate the said option.