Blue is business casual. Always a safe bet, blue can be worn with anything, because it can be interpreted as a neutral in almost any shade except perhaps the most vibrant of jewel tones. Purple, on the other hand, is very particular. It is lush and opulent. Decisive and daring. Paring a bright purple with a toned-down blue allows the purple to shine, and take its place in the spotlight, just as it deserves. Of course, the opposite works as well. A pastel violet will work very nicely with a bold cobalt, lending a sweetness to something vivid, yet even in this context, the violet will be dominant, because purple is so very powerful, and blue so very accommodating.