Colour theory helps us find colours that compliment each other. On a colour wheel, find colours that are on opposite sides of the circle, these are complimentary. Find complimentary colours in the real world and you have the start of a good image.
The colour wheel. Colours on opposite sides of the wheel are complimentary.
The red and orange of the setting sun compliment the blue of the sky. Look at colours on opposite sides of the wheel for drama.
Look at adjacent colours for harmony and peace.
Or look for colours from around the wheel.