From the color scheme, I assume the author of the utility really liked Squeak.
The reason why so many early 1990s UIs have this kind of color scheme is part fashion and part technological opportunity.
Rainbow pastel colors were really popular around 1986 - 1993. It was a reaction to the muted browns and oranges that characterized '70s and early '80s design, and also a reflection of the economic optimism of the era.
At the same time, computer displays evolved beyond monochrome (original Mac) or garish 16-color palettes (PC EGA). With 256 colors out of a palette of millions, it became possible to display those fashionable pastels on a computer too. So why hold back?
(Personally I'm still stuck in this era. Light background is a must. I never use dark mode on anything. I genuinely don't understand the kids who want their IDEs in black like some depressing 1982 textmode VAX. For me it's warm pale yellow and baby blue terminals all the way; extra bonus for dark purple text highlights and a mint green piqué shirt.)
Dark mode is fundamentally a hack around two things.
First, shitty screens that can't run light mode anywhere near dim enough once the sun goes down (which is at least a 5-nines percentage of all screens ever produced). A good chunk of this is due to insufficient PWM frequency but software has a lot to do with it too- and if I can't make the screen go dark enough, well, then I'll just tell all the pixels to be black and use white text.
Second, shitty flat UI design has made it more difficult to see borders between items. It seems to be easier to pick out a bright glowing spot in a field of black than the reverse- it's worse for comprehension, but not for identification/differentiation. It's easier to see that something is selected when you're using white-on-black, and if you already have a good idea what that something is the comprehension penalty is irrelevant.
Those two things predate most proper dark mode implementations; I assert they created the need for it to exist in the first place.
Kid here (34). My understanding is our generation grew up spending much more time looking at a screen in general. Gaming, socializing, following news, doing work, doing homework, talking to parents, talking to partner(s), reading books, painting, sculpting, paying taxes, managing finances, applying jobs, applying for visas... The list is too long to fit here. Participating in society demands more screen time than ever.
Dark mode makes screens blend with the environment better by emitting light where only needed. Since we can't reduce our screen time without any compromise, we try to optimize with the dials we are left with, in this case, pixel brightness.
Admittedly this theory is only backed by personal preference and some vague recollections of CRT-era ergonomics discussion in 1990s UI design books.
Same for my argument too.
There is also the cultural factor. The age when I was going to make a decision about which high school to choose and what kind of study to pursue, we had the chance to enjoy the release of a few of the best sci-fi movies/shows ever made. Those movies had the black screen, neon green/blue strokes and fonts as the main design language. Looking at the letters falling down in the movie Matrix, it was like "coooool, I wanna be able to type those in real time and make computer do stuff".
Now with floaters I have to use dark background and many games are now unusable as they have light background and medium unreadable text and strain my eyes.
My personal theory is that some people are just genuinely more light-sensitive than others, but that the main factor is which scheme came (back) into fashion during someone's formative years, so it will always be associated with being new and novel to that person.
In terms of practicality:
- Dark mode uses less energy and doesn't burn your eyes at night.
- I've only ever found light mode useful when the ambient light is really strong, e.g. direct sunlight shining on my laptop screen. When this happens dark mode is basically impossible to read even with full screen brightness.
So 99.9% of the time dark mode will suit my needs better.
When Americans first got easy access to refrigeration and food became significantly cheaper, we got jello casserole. People would suspend literally anything in jello because it was so novel at the time. Bright, colorful, wobbly abominations. Just like this UI.
Do you have any examples? Because from the early 1990s I only remember Windows pre-XP (mostly black and white and blue), AmigaOS (mostly gray, including the newer frameworks like MUI), NeXTStep (gray). Only exception: the colored tabs in OS/2 Warp, if I remember correctly.
http://toastytech.com/guis/irix.html
It's more muted, but follows the principle of "let's use these truecolor hues now that we've got them."
The global fashion trend after 1990 was moving away from bright pure colors and towards increasingly muted pastels. So for examples of more bright-colored UIs on 256-color displays, I think the Mac II / System 6 era would be the place to look. Early CD-ROMs might be a rich vein.
It is the windows 3.1 aesthetic on much more capable hardware.
Edit: never mind. The link by pavlov has more examples.
It's a reflection in UIs of Memphis Design, which dominated the 1980s: https://en.wikipedia.org/wiki/Memphis_Group
CDE had different default color schemes from different vendors but most of them were pretty colorful in pastel hues.
I actually liked it better than CDE.