Dark backgrounds with light print reduces eyestrain on a screen. If done correctly, it also reduces glare and reflection on a gauge. This is why computer programmers use dark themes and why aircraft cockpit gauges have dark backgrounds and white text.
Are you frequently in well lit environments or places with bright objects?
I started using dark mode in some places well before I knew it was a trendy thing.
I like the brightness of my monitor to be as close to my surroundings while still being able to see it, and that seems to reduce eye strain for me. This means light but not too bright screens in the day and dark screens at night. I'm wondering if I'd be better of with darker screens in the day, but haven't tried yet.
I love the look of the fine black text on the white background of my Interrapid indicator, but I think it's easier to read my black background BesTest.
I have a black face B&S travel and test indicators. I only use them when I need a second indicator set up. I much prefer the white ones. The half colored face would have been nice when using a mirror, but I just put a sharpie mark on the plus side.
My favorite test indicator for working inside a machine is a Vyndicator. A little larger than a standard test indicator but it has a remote readout box.
I find them all pretty equally easy to read. But I have pretty good eyes. I've probably got an equal number of white face with black numbering/needle and black face with white numbering/orange needle. I'm more partial to brand than coloring.