When deciding what colours to use in your space it is good to know what moods they can evoke.  Blue and greens used in a bedroom are calming and lower blood pressure.  They can improve the quality of your slumber.

Red is used in workspaces and dining areas as it stimulates brain activity and appetite.

Violet is associated with royalty and wealth.  It is used to symbolize power.  Violet suggests the owner is confident and stylish.  It is also good to use in a room for meditation but is not a good colour for someone depressed.

Yellow is associated with warmth, intellect, imagination and encourages creativity.

Orange encourages socialization and is good when used in gathering spaces.

If you have a room with poor lighting, warm colours will make the room appear brighter.  When used in darker tones the room will feel smaller.  Warm colours also reflect light so the room will feel hotter.  They look better by lamplight in a room used at night.

Cool colours absorb light so the room will feel cooler.  Cool colours will expand a small space. They also look best in a room used during the day such as a breakfast room or a sunroom.

A long narrow room can be visually reproportioned by painting the two end walls a darker colour.  This will draw the two ends of the room toward the middle.