Designs can be everything.Colours are also one important factors in design.Here are the meanings of colours.

Red:
Red is the color of fire and blood,so it is associated with energy, war, danger, strength,power,determination as well as passion,desire,and love.Red has very high visibility,which is why stop signs,stoplights,and fire equipments are usually painted red.In heraldry,red is used to indicate courage.It is also a color found in many national flags.

To be more specific:
Light red represents joy,passion,sensitivity,and love.
Pink signifies romance,love,and friendship.It denotes feminine qualities and passiveness.
Dark red is associated with vigor,willpower,rage,anger,leadership,courage,longing, malice and wrath.
Brown suggests stability and denotes masculine qualities.
Reddish-brown is associated with harvest and fall.

Orange:
Orange combines the energy of red and the happiness of yellow. It is associated with joy, sunshine, and the tropics.Orange represents enthusiasm, fascination, happiness, creativity, determination, attraction, success, encouragement and stimulation.Orange increases oxygen supply to the brain, produces an invigorating effect,and stimulates mental activity. As a citrus color, orange is associated with healthy food and stimulates appetite.Orange is the color of fall and harvest. In heraldry, orange is symbolic of strength and endurance.

To be more specific:
Dark orange can mean deceit and distrust.
Red-orange corresponds to desire, pleasure, domination, aggression, and thirst for action.
Gold evokes the feeling of prestige. The meaning of gold is illumination, wisdom, and wealth. Gold often symbolizes high quality.

Yellow
Yellow is the color of sunshine. It's associated with joy, happiness, intellect, and energy. Bright, pure yellow is an attention getter, which is the reason taxicabs are painted this color. When over used, yellow may have a disturbing effect; it is known that babies cry more in yellow rooms. In heraldry, yellow indicates honor and loyalty. Later the meaning of yellow was connected with cowardice.Men usually perceive yellow as a very lighthearted, 'childish' color, so it is not recommended to use yellow when selling prestigious, expensive products to men – nobody will buy a yellow business suit or a yellow Mercedes. Yellow is an unstable and spontaneous color, so avoid using yellow if you want to suggest stability and safety.

To be more specific:
Dull (dingy) yellow represents caution, decay, sickness, and jealousy.
Light yellow is associated with intellect, freshness, and joy.

Green
Green is the color of nature. It symbolizes growth, harmony, freshness and fertility. Green has strong emotional correspondence with safety.Dark green is also commonly associated with money. Green has great healing power. It is the most restful color for the human eye; it can improve vision. Green suggests stability and endurance. Sometimes green denotes lack of experience; for example, a 'greenhorn' is a novice. In heraldry, green indicates growth and hope. Green, as opposed to red, means safety; it is the color of free passage in road traffic.

To be more specific:
Dark green is associated with ambition, greed, and jealousy.
Yellow-green can indicate sickness, cowardice, discord, and jealousy.
Aqua is associated with emotional healing and protection.
Olive green is the traditional color of peace.

Blue
Blue is the color of the sky and sea. It is often associated with depth and stability. It symbolizes trust, loyalty, wisdom, confidence, intelligence, faith, truth, and heaven.
Blue is considered beneficial to the mind and body. It slows human metabolism and produces a calming effect. Blue is strongly associated with tranquility and calmness. In heraldry, blue is used to symbolize piety and sincerity. Blue is a masculine color; according to studies, it is highly accepted among males.

To be more specific:
Light blue is associated with health, healing, tranquility, understanding, and softness.
Dark blue represents knowledge, power, integrity, and seriousness.

Purple
Purple combines the stability of blue and the energy of red. Purple is associated with royalty. It symbolizes power, nobility, luxury, and ambition. It conveys wealth and extravagance. Purple is associated with wisdom, dignity, independence, creativity, mystery, and magic.According to surveys, almost 75 percent of pre-adolescent children prefer purple to all other colors. Purple is a very rare color in nature; some people consider it to be artificial.Light purple is a good choice for a feminine design.

To be more specific:
Light purple evokes romantic and nostalgic feelings.
Dark purple evokes gloom and sad feelings. It can cause frustration.

White
White is associated with light, goodness, innocence, purity, and virginity. It is considered to be the color of perfection.White means safety, purity, and cleanliness. As opposed to black, white usually has a positive connotation. White can represent a successful beginning. In heraldry, white depicts faith and purity.

Black
Black is associated with power, elegance, formality, death, evil, and mystery.
Black is a mysterious color associated with fear and the unknown (black holes). It usually has a negative connotation (blacklist, black humor, 'black death'). Black denotes strength and authority; it is considered to be a very formal, elegant, and prestigious color (black tie, black Mercedes). In heraldry, black is the symbol of grief.