How to color an indicator based on alert conditon

This is what I want to do. I want to take a donchian channel and have the channel change based on a 3 and 12 bar simple moving average.

For example if the 3 bar moving average is > than the 12 bar moving average I want the top channel of the donchian channel to be hidden so that only the lower channel is showing on the chart. If the 3 bar moving average is < 12 bar moving average then I want the bottom channel hidden. It will kind of look like a parabolic when finished.

Any help on this would be appreciated incredibly. Thanks.

Regards