The National Falls

I am keen for some feedback on this image, particularly regarding any colour cast - I do have a calibrated monitor, yet I find some images (waterfall/ lots of green i the scene) often have a slight purplish tinge, i do notice this when using a CPL and a light ND (3 stops) and usually correct for it by adjusting the colour balance (yellow and red) however this image had only the CPL on and I thought I removed any telltale signs of the tinge, thoughts? click through to flickr for a larger resolution version. AutoWB btw 
National Falls by Gerard Blacklock, on Flickr

