Why is the world losing color?

It's not "losing" color.

At periods when technology resulted in new color possibilities, people went overboard with color. Make all the things colorful!! Think of the technicolor sixties. And we can go back in history and see the same thing with new clothing pigments, new paint pigments.

But when everything is colorful, nothing stands out. Everything being colorful is as monotonous as everything being, well, monotone.

Modern taste is more about more neutral-colored foundations with color accents. Don't paint a whole room green -- have a gorgeous green plant that stands out all the more against its neutral background. Don't paint a whole wall orange -- have a beautiful orange-hued piece of art on the wall. It's just more tasteful to use color as one element, along with size, shape, texture, and so forth. Making it the main element in everything is just overdoing it. It's bad design.

I don't want constant "riotous color", as the article puts it, in my home, or my workplace, or while I'm driving. It's visually exhausting.

You can see the same thing in music recordings during the 60s. Stereo and quadrophonic sound was new so everything was panned all over the place really hard. Drums all on the left, vocals hard right etc. It's an interesting effect sometimes, but generally a gimmick and/or distraction. We don't really do that anymore, for good reason.