Here's a simple tip on the use of colour in picture design. Red is a powerful and emotive colour. Red is used to warn people of danger, to attract people's attention and its the colour of blood! Nature uses red - birds use it to adorn plumage, spiders use it to warn of danger and the Proboscis monkey in Borneo uses it to attract a mate.
But use it sparingly! Too much red or too many powerful colours in an image and the dramatic pull of red may be lost. Also, try to avoid something unimportant (the bucket in the corner of the family portrait) being red as the viewer's eye will go to that.
My artist neighbour John Manson once gave me this advice 'Keep it plain, almost bland with a small dollop of red ... and you'll never be far wrong!'