Also unix commands tend to have illegible colors in Powershell on Windows. (Ripgrep for example). Powershell defaults to a blue background.
I would suggest these rules for using default coloured output:
1. Don't.
2. Really, don't. Bold is fine, though!
3. (experts only) Make sure the colour scheme works with white-on-black, black-on-white, white-on-navy (for powershell), and Monokai/Solarized/whatever the flavour of the month for insecure hipsters is.
If you use colours, by default or not, make it really easy to configure the colours, so people can make it work with their terminal's colour scheme.
[1] - https://github.com/BurntSushi/ripgrep/blob/acf226c39d7926425...
The issue I've found is that of the 16 build in colors. cmd defaults to trivial colors. (eg Blue is 000080 and Bright blue is 0000FF.)
Which give terrible contrast. MS seems to be working on improving things on their end. Then I'll be able to make it readable. (Eg: https://github.com/Microsoft/console/tree/master/tools/Color...)
Also for colors it's good to try to pick a decent palette of a couple-three colors and stick with it rather than try to categorize a bunch of different bits of output on a single command.
Still, colors are awesome and make your CLI look and feel 10x better than it is, so it's worth the extra effort.