A good way to select colours for your garden is to use the Colour Wheel. The Colour Wheel helps you identify which colours will work together. The Colour Wheel visually expresses the relationships between colours.
Contrasting colours are any two colours opposite each other on the Colour Wheel. For example: green and red, blue and orange, purple and yellow.
Harmonising colours are close to each other on the Colour Wheel. For example: yellow and green or different shades of the same colour.
Triadic colours are at 60 degrees to each other on the Colour Wheel. For example: orange, green and purple or red, blue and green.
Warm colours are colours associated with fire (or the sun) such as red or orange.
Cool colours are colours associated with ice (or water) such as blue.