The pie chart has two styles, one that it uses when slices are deselected (pie.style) and one it uses when slices are selected (pie.selectedStyle). So to get your slices to be the same colour at all times, try the following:
pie.style.flavourColors = myColorArray;
pie.selectedStyle.flavourColors = myColorArray;
EDIT: I made a mistake in the code, it is now updated!