iMessage colors

This is probably a stupid question but when i use iMessage i noticed that not all of my chat bubbles are the same color. When i send messages they are blue and for the majority of contacts the messages i receive are white, but for a select few they are purple and blue. I checked preferences in iMessage and its set to automatic. Is there some way to set a color to a specific contact?

 

I mean I know my messages are supposed to be blue, and I know incoming are supposed to be this white, but the incoming on just a couple are purple or blue and it's constant. They are always the same color even if I delete the message and start a new conversation. Almost like there should be a setting that would allow me to select the color I want for a specific contact. Is that possible is what I'm getting at? I know I can change all of them to a single color but can I set a single color to a single contact?