There’s an old, old joke: The man with a clock knows what time it is. The man with two clocks is never quite sure. Read one article on color theory, and you know color theory. Read two articles on color theory, and you no longer know anything.
Most writers would probably agree that orange + purple is not a felicitous combination. Beyond that, you get into arguments.
Most people in possession of normal eyesight would agree that large areas of #0F0 are not suitable or appropriate for, well,
anything. Except possibly a “no hotlinks” message when your intention is to make it look horrible, the horribler the better.
Most rational people would agree that 60% grey is not a suitable color for your primary text, especially if it is intended to be read by grownups. This leads to the conclusion that a great many web pages were designed by non-rational people.
You can always spend time at [
webpagesthatsuck.com...] for plentiful ideas of what
not to do. The site hasn’t been updated in three years, but what was true in 2016 remains true today.