Well, I sort of agree… that is, many people’s tastes are strongly affected by what they are told is valuable/best/”the norm” by others (and they usually don’t realize it) …and it’s really impossible for any color on the visible spectrum to be objectively “ugly”.
But, I wanted to say that nobody just came up with having colorless (D) diamonds as being the most costly on the D-Z scale. They are not actually the most costly color – pure stoplight red is the most costly color of natural diamond, because they are the most rare. After that, fancy pinks, blues, etc… (natural ones I mean, not the irradiated ones in the stores these days…those are usually pale yellow naturally). They are all extremely uncommon, and even vivid canary yellow is less common than D colorless, so it commands a higher price, even though it is “yellow” and some of the most affordable diamonds are “yellow” too. The most common natural colors for diamonds are pale yellow, gray, brown, and black, so these are the most affordable. It’s supply-based, in part.
Another part of it is that as a very general rule, people tend like vivid “colors” vs. more muted ones. I say “colors” because bright white is one of them, though it technically isn’t a color. So this is affecting demand.
Next is the fact that some colors tend to be more popular colors than others. Ask someone what their favorite color is, and you’ll hear “blue” many times more than you’ll hear “brown”. Though you will hear “brown” if you ask enough people, and I don’t believe there’s any color that’s universally hated. As for “white”, people don’t often think of it as a “color”, but if you look at the number of white things people tend to purchase, own, and use, it’s not hard to see why bleach is so popular an invention. Demand is affected here too.
So yes… do norms affect what people see as valuable/attractive? Absolutely. It’s not hard to think of many ridiculous trends people have spent good money on, probably even ourselves (just think back to junior high) . But it is hardly the only factor going on in this instance, or even the most substantial.