How to lock colors on the chart

I have a pie-chart in excel (and powerpoint) with 4 wedges. Is there a way to lock certain colors for certain wedges?
The reason is I'm showing same chart with a wedge expanded into 2 wedges, than further and further and I would like to have a consistent look throughout the slides.

E.g.
chart 1
1- green
2 - blue (lock)
3 - orange (lock)
4 - red (lock)

chart 2
1.1 - purple
1.2 - light green
2 - blue (lock)
3 - orange (lock)
4 - red (lock)

right now excel refreshes the coloring to default