Your should declare colours
object as an array
"colours": [{
fillColor: 'rgba(47, 132, 71, 0.8)',
strokeColor: 'rgba(47, 132, 71, 0.8)',
highlightFill: 'rgba(47, 132, 71, 0.8)',
highlightStroke: 'rgba(47, 132, 71, 0.8)'
}];
For more info refer this post / this too.
For newer versions, see eli0tt’s answer, as the parameter names have changed.