Great thoughts. Thanks for taking the time to express them thoroughly.
Personally, I find that a simple color pallet helps to express information on a computer display. I would limit it to no more than half a dozen distinct colors, max. I find it frustrating (and makes me angry) if I need to distinguish between, say, “Green”, “Teal”, “Emerald”, etc. Or differentiate based on the characteristic sometimes called “saturation”.
But when I move from computer display to paper copies . . . . the great majority of printing is done in monochrome. Yea, verily, as I sit at this workstation at this very moment, my computer monitor has a schematic in one window, and two paper copies of that schematic are on the worktable. (The paper copies are annotated with measured values, waveforms, thoughts and ideas, summaries of calculations, etc.) OK, so I’m the superannuated guy who started work when blueprints were blue, and smelled of ammonia from the reproduction process. But I see co-workers half my age doing the same things.
My point is, don’t depend on color to be the primary way to distinguish types of labels. I think you agree, which is why you selected several graphic shapes to go along with the colors. Yeah, they bear a resemblance to the graphics in a certain commercial simulation program, and I wonder if there is either a formal standard, or a de facto gentlemen’s agreement among CAD/CAE developers regarding what the shapes should be and how they are used.
As an alternative to your ideas, I might propose that the same shapes could be used for two of the symbol groups (“Global” and “Sheet”; or “Sheet” and “Local”) but make the shape outlines either solid lines, or dashed. Maybe even solid, dashed, and dotted, though that’s getting similar to the problems with “Green”, “Teal” and “Emerald”.
Dale