Trying to define aura colours is complicated just because we don't all perceive colours or emotions the same way.
For people who are just learning how to understand what each colour represents to them, it is usually wise to keep with the 7 main colours until you are comfortable with what you are perceiving. I've gone ahead and posted some of the more common colours and their associated emotions, but as I said they may not necessarily fit with you. Best way to learn is to start practicing with people you trust and talk to them about the colours you are seeing and how the person is feeling.
General colours
Red: lust, anger/hatered, love, courage, passion
Orange/Brown: active (sexually or physically), very focused, goal orientated, motivated, works with earth/nature
Yellow: inteligence, friendship, fear, embarassed, illness, mischievous
Green: prosperity, fertility, jealous, illness or healing
Light Blue: insparation, peace, tranquility
Dark Blue: emotional friction, turmoil, stress
Purple: healing, cleansing, transition
White: purification, healing, protection, enlightenment
Black/grey: illness, misery, unfocused, bad luck, works with earth/nature
Gold: success, good luck, enlightenment
Pink: unconditional love, friendship, healing
