I can remember when I first began to take an interest in aura's, I read somewhere (no one ask me where, I can remember the website), I came across a site that stated that often blue aura's have emapthy. I go through periods myself with strong empathy, than it fades away. It depends really on my level of interaction and close-ness with people.empaths is a great place to start with any with emapthy.
Most people I've noticed who received a high score in a blue aura also have high lavender and indigo. It makes sense considering a lot of traits that indigo and lavenders have, blue's also have. Personality traits and such.