Are blue squares for squares? Who cares? Ski resorts build “intermediate” slopes to serve the majority of their patrons -- people who still have a lot to learn, or people who do not care to tease death too much. Ski blue trails when you are ready. (Typically not one's first day on skis.)
Every ski resort or area designates its terrain differently from its competitors. A black diamond at one hill is a blue square at another. Be aware of this. Pay close attention to trail layout on any ski resort's trail map. And never just “point your skis and go” down any ski slope you have not skied before. Take a look ahead first.
Know-it-all kids (the kind you are likely to come across on any weekend at a ski resort) with any ability think green circle -- or beginner -- ski slopes are for wimps. What if they are right? So? Be a wimp. Green slopes ski great (and even greater sans crowds on weekdays, or any day if you do the right thing and take lessons). You can challenge death on harder trails as you learn to ski better than the snotty kids. And take heart. People crash and die on beginner ski slopes, too.
What's the difference between a black diamond ski slope and one assigned even more diamonds? Possible death and certain death. Ski a black diamond trail and you may experience mild death or dismemberment by trail's end. Run a ski slope with a diamond or two extra and you should expect a messy death just a few feet from the start.