1.3.3 Sensory Characteristics
Don't tell people to take the fucking red pill, and not just because that shit was co-opted by sweaty basement twats with guns and anger issues. Giving people instructions that rely on color is shitty. Generally assuming people can see whatever random pixel vomit happens to be displayed on the screen is also shitty. Also don't assume everyone can hear shit.
So writing "use the settings icon" is fine if you have an icon labelled "settings", but writing "click on the icon shaped like a gear" is crap. "Use the settings icon, which is shaped like a gear" is good, though.