Color of energy is based off of perception, it is not like the physical where color is consistent due to wave lengths of light. Especially when observing auras people will see different colors that reflect their own interpretation of the energy and their own view points on what those colors mean. Color meanings can greatly differ from culture to culture. So its important that when someone looks at our aura and tells us the color(s) they see that we ask what that means to them.
Also, I'd also like to add that aura color can change with our moods. When I'm very angry, my aura turns black and when I'm meditating or practising magick it is usually more white. The rest of the time I usually have a deep blue all around with some purple by my head. I have been told I can't conceal my emotions, and apparently neither can my aura. Haha, joke? Ok, shake your head at my corny attempt at humor.
Anyway, I really don't put much importance on auras unless it looks/feels dirty, damaged or irregular in shape and size. A good size, strong, clean, consistent aura is really all that matters.
And as for auras working off one another, yes they do. When people are in love, their auras tend to mingle. When someone has wild or very prominent energy that doesn't sit in one place but fills every room they walk into, well it isn't good, but it tends to provoke change in other people's auras as they subconsciously react to the person's energy. And when people invade others personal space / personal "bubble" the reaction is greater. Our auras are a reflection of the mind, emotions, and spirit of each individual (and sometimes even physical health) and we all know energy can effect these, so of course a strong resonance of energy from another person can effect others around them for better or worse. Some people "light up a room" and others can "bring down" those in the same vicinity.