Now you are being silly, deliberately snipping the majority of the paragraph to (try to) make a point.
That is honestly how I parsed it. Perhaps I misunderstood what you meant by a "hint", versus the opposite of my "necessary"?
As an example, consider a schematic where positive supplies, negative supplies, ground, high-frequency digital, audio-frequency analog, and almost-DC control signals are all drawn in slightly different shades. (I discovered that using completely different colors is too heavy-handed, except for supplies with reds and blacks; distracting rather than helpful. Consider sufficiently dark pastel colors on white background, or light on dark background.)
For components, I don't like bypass capacitors being stuffed separately in some corner. I'd much prefer them to be nearby the pin they're supposed to be even in the schematic, but drawn with less contrast compared to other capacitors in the schematic. (I found that for myself, drawing them e.g. smaller than other capacitors is more distracting than helpful.)
Try these and see for yourself. Take one of your own projects, plot/export the schematic as SVG, and open it in Inkscape. Select all, and repeatedly Object > Ungroup (Shift+Ctrl+G) until no more groups left, and you can edit individual traces and objects. When you select some tracks, use Path > Combine (Ctrl+K) to combine them into a single object, so you can use Object > Fill and Stroke to select its color. Set Fill to None, and Stroke to the color and opacity you want.
I don't think these are "hints", because the idea is not to convey extra technical information about the schematic, or the designer intent behind parts of it; it is only to help humans perceive and understand it more clearly. The additional information is not
necessary on top of what the schematic shows if simplified/converted to black and white only, it is only there to reduce the cognitive load when trying to parse/read/understand the schematic.
I see "hints" more like the comments delineating a subsection saying "pre-regulator" or "filtering", explaining the designer idea behind the schematic, somewhat similar to code comments in software. I'd never use color to convey that kind of "hints". I'm sure my understanding of the way others use the terms differ, but
you don't seem to bother to try and define them. I guess "everybody knows what a hint is!", eh?