I worked on a project that was using shades of grey for everything before we hired a designer. It was terrible and illegible and designed by our boss who I’m am entirely convinced has aphantasia.
Someone started complaining that two pieces of text weren’t the same color. They were exactly the same color though. We’d built an entire UI full of optical illusions.
This has a lot to do with framing in photography, architecture, and all these other things where "design" is involved that humans perceive as pleasing. It also means that not everyone has a knack for that. In return, chances are good that there are ways to actually "calculate" it. One well known example: The golden ratio that shows up in many designs, architecture, framing etc.
