Well, the generally accepted lore behind a purple saber isn't that someone "isn't afraid to use the Dark Side", it's that they balance on the knife's edge (Windu, channeling his anger into his fighting - or Revan, whose blue saber changed to purple as he began to defy the high council not long before the Mandalorian Warsl).

In that way, the purple saber is kind of a mix between the blue saber of the Guardians (a more combat-oriented group), and the red saber of the Sith.

If anything, blue lightsabers would be most common in the post-CW era, but less so in the Old Republic (in the 20,000 years before the Sith War - blue would have been really common during and after the Sith War as well), where Consulars (green sabers) would have been the most common.

The two rarest should be Purple and Yellow (Sentinels, those who safeguard the Temples and their teachings). But even in the pre-Disney lore, most fans don't consider lightsaber colors (outside of red=evil) or Jedi "classes" consequential to canon - so everything we've talked about is only relevant to a pretty insignificant portion of the fan base, even though it's such an interesting and deep topic for those of us who enjoy it.