This is a very good question...we live in a world of energy sometimes named chi, ki, life force energy...all aspects of our physical world that we can see, hear, touch, smell and taste are accompanied by a flow of subtle electromagnetic energy. This energy circulates in our bodies through the system of chakras and meridians and feeds itself on our thoughts, ideas, emotions and our dreams. This explains why positive thoughts are so important they nourish the chi, negative thoughts destroy and can act like poisons. Not only does the chi circulate within our bodies, it also forms the aura surrounding our bodies, extending from 10c.m to 100c.m. and sometimes more. The color of the aura is constantly changing reflecting our thoughts, emotions and ideas, that is how some people are actually capable of "seeing" what we are thinking. The chi is very sensitive and easily influenced, not only does it reflect our inner state it is also easily influenced by the ambient chi, one reason why it's best to wear cotton and other natural fibers, it allows a better flow of energy,

well who tell you that your aura is blue? usely you have alot more then 1 color. you have at least 4 colors.with different position of the colours different density and shades of colors and some have a black line in the aura also. maybe those negative emotion are that black line.

AURA COLOR MEANINGS

RED AURA COLOR: Relates to the physical body, hart or circulation. The densest color, it creates the most friction. Friction attracts or repels; money worries or obsessions; anger or unforgiveness; anxiety or nervousness

Deep Red: Grounded, realistic, active, strong will-power, survival-oriented.

Muddied red: Anger (repelling)

Clear red: Powerful, energetic, competitive, sexual, passionate

Pink-bright and light: Loving, tender, sensitive, sensual, artistic, affection, purity, compassion; new or revieved romantic relationship. Can indicate clairaudience.

Dark and murky pink: Immature and/or dishonest nature

Orange Red: Confidence, creative power

In a good, bright and pure state, red energy can serve as a healthy ego.

ORANGE AURA COLOR: Relates to reproductive organs and emotions. The color of vitality, vigor, good health and excitement. Lots of energy and stamina, creative, productive, adventurous, courageous, outgoing social nature; currently experiencing stress related to apetites and addictions;

Orange-Yellow: Creative, intelligent, detail oriented, perfectionist, scientific.

YELLOW AURA COLOR: Relates to the spleen and life energy. It is the color of awakening, inspiration, intelligence and action shared, creative, playful, optimistic, easy-going.

Light or pale yellow: Emerging psychic and spiritual awareness; optimism and hopefulness; positive excitement about new ideas.

Bright lemon-yellow: Struggling to maintain power and control in a personal or business relationship; fear of losing control, prestige, respect, and/or power.

Clear gold metallic, shiny and bright: Spiritual energy and power activated and awakened; an inspired person.

Dark brownish yellow or gold: A student, or one who is straining at studying; overly analitical to the point of feeling fatigued or stressed; trying to make up for "lost time" by learning everything all at once.

GREEN AURA COLOR: Relates to heart and lungs. It is a very comfortable, healthy color of nature. When seen in the aura this usually represents growth and balance, and most of all, something that leads to change. Love of people, animals, nature; teacher; social

Bright emerald green: A healer, also a love-centered person

Yellow-Green: Creative with heart, communicative

Dark or muddy forest green: Jealousy, resentment, feeling like a victim of the world; blaming self or others; insecurity and low self-esteem; lack of understanding personal responsibility; sensitive to perceived criticism

Turquoise: Relates to the immune system. Sensitive, compassionate, healer, therapist.

BLU AURA COLOR: Relates to the throat, thyroid. Cool, calm, and collected. Caring, loving, love to help others, sensitive, intuitive.

Soft blue: Peacefulness, clarity and communication; truthful; intuitive

Bright royal blue: Clairvoyant; highly spiritual nature; generous; on the right path; new opportunities are coming

Dark or muddy blue: Fear of the future; fear of self-expression; fear of facing or speaking the truth

INDIGO AURA COLOR: Relates to the third eye, visual and pituitary gland. Intuitive, sensitive, deep feeling.

VIOLET AURA COLOR: Relates to crown, pineal gland and nervous system. The most sensitive and wisest of colors. This is the intuitive color in the aura, and reveals psychic power of attunement with self. Intuitive, visionary, futuristic, idealistic, artistic, magical.

LAVENDER AURA COLOR: Imagination, visionary, daydreamer, etheric.

SILVER AURA COLOR: This is the color of abundance, both spiritual and physical. Lots of bright silver can reflect to plenty of money, and/or awakening of the cosmic mind.

Bright metallic silver: Receptive to new ideas; intuitive; nurturing

Dark and muddy gray: Residue of fear is accumulating in the body, with a potential for health problems, especially if gray clusters seen in specific areas of the body

GOLD AURA COLOR: The color of enlightenment and divine protection. When seen within the aura, it says that the person is being guided by their highest good. It is divine guidance. Protection, wisdom, inner knowledge, spiritual mind, intuitive thinker.

BLACK AURA COLOR: Draws or pulls energy to it and in so doing, transforms it. It captures light and consumes it. Usually indicates long-term unforgiveness (toward others or another) collected in a specific area of the body, which can lead to health problems; also, entitities within a person's aura, chakras, or body; past life hurts; unreleased grief from abortions if it appears in the ovaries

WHITE AURA COLOR: Reflects other energy. A pure state of light. Often represents a new, not yet designated energy in the aura. Spiritual, etheric and non-physical qualities, transcendent, higher dimensions. Purity and truth; angelic qualities.

White sparkles or flashes of white light: angels are nearby; can indicate that the person is pregnant or will be soon

EARTH AURA COLORS: Soil, wood, mineral, plant. These colors display a love of the Earth, of being grounded and is seen in those who live and work on the outdoors....construction, farming, etc. These colors are important and are a good sign.

RAINBOWS: Rainbow-colored stripes, sticking out like sunbeams from the hand, head or body: A Reiki healer, or a starperson (someone who is in the first incarnation on Earth)

PASTELS: A sensitive blend of light and color, more so than basic colors. Shows sensitivity and a need for serenity.

DIRTY BROWN OVERLAY: Holding on to energies. Insecurity.

DIRTY GRAY OVERLY: Blocking energies. Guardedness

http://www.reiki-for-holistic-health.com/auracolormeanings.html

experience and enjoy.

i dont have any practical knowledge of aura, or how to change them if they can be changed directly. but as far as i know, emotions are under your direct control, atleast inherently. but one needs to regain that control. and this can be done through various practices easily, but needs patience. once emotions are under your control, your aura naturally will change towards the better. and when you say blue, you may be right that you are a peaceful person, but peacefulness will not be your (only) emotion/mental condition 24 hours a day. even you agreed to that. even one thought of anger will add a little redness to your aura (i guess), because it does give out thoughts of red colour. so practically, as per my limited knowledge, aura is just a sum of all your emotions. to a person with an activated third eye, it may tell everything, especially your emotion at that very instant. but for the person himself (i.e. you), more that the colour, it is the awareness of the very emotionn, every emotion, every thought, every moment, that will matter, practically, so that you can work on improving them...

I'm no aura expert aren't they in a constant flux the hue might stay a certain color but the intensity changes with the emotions? and as a person grow the aura changes also .. kinda like get old and turning grey.
peace