3. Automatic tools and sliders can only go so far. When discoloration remains, you have to get in there and remove it manually. Duplicate your Background Layer, then zoom in on the purpleringed branches. Type the letter O on your keyboard for the Sponge tool (if you don't see it, it's hiding under Dodge or Burn in the main Toolbar). Then, in the Options Bar, choose Mode: Desaturate. Paint over the purple to start cleaning up the branches. Don't worry if you have a messy, heavy hand. Because the branches are almost in silhouette, they're nearly monochrome anyway. Just be careful not to desaturate any leaves. If you accidentally lose color you want, add a mask to the layer and paint with black to reveal the properly toned Background layer below.