I see these all time. It doesn't have to be around people and it happens just about anywhere..
To add a little bit of theory to this topic, I always see black or dark orange color bursts around people that don't like me. Also, when I am with friends, the color bursts are much smaller and lighter.... Maybe it has to do with the energy people are sending you.
Usually though, I know this, whenever I see one (or many multiple ones) I have distinct feelings. So for example, in bed yesterday I was thinking happy thoughts while shielding myself and I saw pure white flashes. Some were stars others were moving and I know it made me feel good and protected - very friendly and safe, playful even.
But when these sparks/flashes are dark colored I always have this empty feeling. Kind of sad and little apprehensive too.
If this has happened to anyone else, please let me know, I am very interested to see what other people have to say.