2017 Pro Edition. Is this as intended?
I'm thinking yes, this is intended.
When you first create a plane it appears in the media pool. Effectively you have created a unique media clip. When you duplicate a plane LAYER you are creating another instance of plane MEDIA. When you change the properties of the plane you are changing the master plane media, therefore changes should propagate to all instances.
This also works the same way in HF2-4.
So to have two planes of differing colors you either create two planes, or use color grading tools (Hue/Saturation, Color Wheels, Gamma, Curves, Levels Histogram, Tint, etc...) to adjust a duplicate instance.
FWIW I tend to only create one or two planes at most of a given size in a project and use color grading effects for different colors. When adding planes to a comp, either duplicating an instance or dragging in from the media pool. I just don't like seeing 20 things named "New Plane" in the media pool.
Fill Color Effect quickly changes colour from a single white plane.
@Palacono d'oh! Fill Color. The easy one I couldn't remember while ten other options went through my mind (... Shadows/Highlights, Color Balance, Color Channels, Color Phase...).
I just don't like seeing 20 things named "New Plane" in the media pool.
Yeah, I noticed that after I'd made a bunch of planes for various shots. I was like "holy crap, this is gonna be a nightmare to organize."
So the explanation makes sense. I guess I was assuming that modifying a duplicate element (adding masks, etc.) was the same as changing a property, and it clearly isn't.