I tried using the Selective Color adjustment layer to reduce magenta, with no success.
Better results using a new layer set to Color blending mode.
Then brush over the magenta stripes using a color sampled from nearby blues.
I resampled frequently as I moved lower in the sky and in the water.
Use a brush with lowered opacity for gradual buildup and blending.
Alternate method for the sky might be to fill with a gradient of blue color sampled from blue at the top and right above the terrain.
forum discussion: http://forums.dpreview.com/forums/read.asp?forum=1006&message=28002383

original image by Bob Altic: