George Lucas has said color was important to the moods created in the movies. Each one having specific colors in their atmospheric themes. Colors are symbolic and induce an emotional response.

Such as In Empire Strikes Back the movie starts in a cold blue and white wasteland. Representing the forboding of the darkness and sadness to come later. Dagobah has a muted colors greys and blacks giving the feeling of mystery uncertainty and dream. A perfect place to learn the spiritual nature of the Force. Even Yoda is a grey-green color. The oranges and sterile whites of Bespin showed a safe haven until the trap was sprung and the colors were mixed with blacks and greys setting a heavier and ominous tone. Giving visual ques to the confusion and turmoil set loose on Luke.
In Return of the Jedi where green is used on Endor's moon showing a natural fertile world and showing the Empire's disregard for life and the Force through their misuse of the planet to build Death Star. Its a place for the viewer to connect and show sympathy. The blacks grey's and reds of the throne room on the Death Star show power, anger, hostility, evil, Lifelessness, curruption of the Force.
Return of the Sith used burgundy and golds to create a sense of regal prosperity and romance. The deep red burgundy became darker as Palpatine revealed himself and Anakin fell giving the sense of blood. The mood quickly became darker as more blacks and fiery oranges / reds are used on Mustafar showing the turmoil, anger and power lust of Anakin. We end the movie in black, blue, indigo, and violets. These suggest a feeling of sorrow, mourning, twilight (made even more so by the candles and flowers in the funeral that twinkle like stars). An ending of day. The fading of light that gives way to the coming night. A which will eventually itself move aside to the new dawn of white, yellow, and golds of Tatooine in A New Hope

In psychology colors can be interpreted as:

Yellow- Happy, warm, bright - Ironicly when used in a room the color yellow can cause people to lose their temper more and babies to cry more frequently.

Orange- Energetic, enthusiasm, attention getting

Red- strong emotions, love, lust, comfort, anger, evil

Purple- Royalty, wealth, wisdom, spirituality, exotic

Blue- Calm, serenity, sadness, aloofness, cold. In usage blue can lower appetite, pulse rate, and body temperature. Some studies have even shown an increase in productivity in blue rooms.

Green- Nature, tranquility, good luck, prosperity, fertility, increased comprehension, and Health (green can help the healing process)

Black- Menace, evil, death, unhappiness, closed, heavy, formality, & sexuality. In color theory black absorbs all light and is created by the combination of cyan, magenta and yellow in what is called subtractive color. It is also associated with submission. (Gives a new perspective to Vader's suit)

White- Purity, Innocence, light, open, cold, bland, sterile, empty. White reflects all colors. Color theory shows white created by the combinaton of the color spectrum in what is called additive color.

Brown- Natural, strength, reliability, isolation, down-to-earth, sophistication
The jedi use brown quite a bit.

The feelings evoked by these colors can be intensified or changed by combinations with other colors. Red when used with black for instance conotate darkness, evil, lust but when mixed with white or pink gives us a feeling of passion or love.

For some more insight on the meanings of color. Some ancient cultures used colors for healing in a process call chromotherapy. Our native american culture (the Sioux spicifically) use color to signify the four sacred directions.

Red- the power of the east where the morning star and sun first arise. The new day, new experiences, youth, knowledge. It is also the color for pipestone which comes from mother earth, the blood of the earth.
Yellow- is the south. it represents growth, the spring, healing.
Black(blue in some tribes)- represents the west where the thunder beings send forth the rain (water). It also represents the spirit world and where the sun sets. It is darkness, release, spirit protecteion
White- represents the north power. It is strength, endurance, purity, truth, contemplation, creativity, courage. It is the white blanket of snow that cleanses and prevents disease. The White Buffalo Calf Woman.

Green- is the representation of Mother Earth

In the vision of Black Elk, he sees a blue man that has come to spred evil and chaos over the earth.

This next part delves into my new age beliefs so anyone who wants can skip to the bottom.
Edgar Cayce "The Sleeping Psychic" spoke of colors as representing different vibratory wave lengths. These waves interacted with one another and could be used (much like the Force) to manipulate the physical world. These fields could be seen around objects as auras and in a larger scale the arora borealis.

Red-body, earth, hell, force, energy, vigor,
---Dark red-high temper and nervous tormoil, domineering, brash
---Bright red-impulsive,active, self centered
---Scarlett-egotistical
---Pink-immature
Orange-sun, thoughtfulness, considerate, glory, virtue
---Golden orange-vitality and self control
---burnt orange-lack of ambition, laziness, and repression
Yellow-
---golden yellow-health well being, worry free, happy, friendly, helpful,
---ruddy yellow-timid, indecisive, weak willed
Green-youthfulness, fertility, nature
---Emerald green is the color of healing, helpful, strong, friendly
---Yellow green weakend deceitful
Blue-color of spirit, contemplation,prayer, heaven, sky, high mindedness, and is said to be the true color of the sun
The deeper the blue the better their influence. They can be unusual and moody but driven and spiritual minded. unselfish.
Indigo & Violet-seekers of a cause or religious experience, The purple stone amythest is a stone of healing and spiritual awareness.( a different take on the Mace's lightsaber debate)
White-perfection, balance of all colors, christ
Grey-sickness and color neutrality.

Cayce also spoke of the five races (colors) of man as representing the five senses.
Black-taste
Brown-smell
Red-Touch
White-vision
Yellow-Hearing
The next race to evolve is said to be indigo-spirit/psychic

I hope this brings a better understanding of the importance of color and how it relates to our world and the feelings Lucas was trying to evoke within the films. Color is a visual connection to energy and emotion. It's getting late and I need to end this so until next time.

"I'm green, and it'll do fine
And I think it's what I want to be" -Kermit

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Here are some more links to artwork, enjoy if you do.

Journeys_Watcher
Journeys_Stealing the Moon (work in progress)
Relativity of Spirituality
Relativity of God, man, and the expanding universe
The relativity of time and movement
Bear Spirit
Journeys_-Wandering-Spirits