It's very old news. It comes from the dayes of olde when computer monitors could display all of 16 basic colours. (About 1985).
For at least the past 20 years, monitors have been able to display 16.3 million colours. So we are told - the human eye can distinguish about three million, so you'll never know for sure if you're being hoodwinked.
Go right ahead and use any colours you want. Just make sure your colour scheme is beautiful and suitable!