Many usability guidelines warn against red
Agree. That's why I use some orange shades. It's not as cold as blue, or boring as grey or black. You may also try green, or - don't laugh - (dark) pink.
The [G]UI is for to improve work efficieny, not for to look "cool" or impress your buddys. Many are not aware of wrong [G]UI settings may tire you quicker. I also used window's transparency for a short testing time. It only looks cool, but according to work efficieny it's contraproductive.
So be careful with picking colours. Using lighter shades are better than having full contrast. A few carefully selected colors are better than having it too coloful. My shells are also light-grey text ond dark-grey background. Looks old-school, since the monitors in the 1980s looked that way, but I find black text on white screens is too shrill when looking all day at it.
Also the combination of dark red, amber and brown may sound uncool, but make a good combination you can work nicely on text (shell/editor) with.
Try some different themes for the syntax highlighting of your texteditor as also as take your time to pick a good font.
my current background
you may find good background pictures when searching for "abstract [colorname] (background)"
Another way to get almost plain but not sterile background pictures is to make fotos of equable surfaces like the sky, sea, beach, walls,...
With your paint program (e.g. Gimp) you can quickly resize them to your screen's resolution, or change it to another basic color.
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By the way I don't look much at those neofetch windows. When I have to use magnifying glasses to read the only line that interests me within all the others, while at the same time almost 50% of the space are for the ASCII-art of Beasty, it's fiddle-faddle to me, so I don't pay much attention.
