Bingo! Now that you jogged my memory, I can confirm this.

The next question is why you need a white outline around the black arrow.

This is easy to answer: if you didn't do that, what would the black arrow look like against a black background?

Some DE solved that by having an inverse outline.

Took me a really long pause to think up what DE meant, so to save others from similar waste “desktop environment”

I'm pretty sure even on windows there is the option of having the whole cursor be the inverse of the background

The format has a special color for it, you can mix inverse pixels anywhere in a classic windows cursor IIRC

And if I'm not wrong, it still applies to today's Mac interface. The cursor still has a white outline all around.

Yup. You can even customise both the inner and outer colours as an accessibility feature!

What??? TIL.

A lot of the accessibility features are actually neat even to those without the need for them.

Yeah, it’s become super useful for me to color code the cursors between my work and personal Macs.

Seriously. Anyone over the age of about 18 should spend a bit of time going through them, there are many useful things (zoom part of screen is a powerful help on macOS for example).