This is the best solution I can offer ...
Add a Channel Mixer adjustment layer, go to the Blue output channel, and change from 0/0/+100 to 0/+80/0.
Then invert the mask, and paint loosely onto the purple areas. Hopefully it will blend well enough to get away with it.
This has nothing to do with the class. Just make sure you do your noise removal exactly as outlined in that article.