photo retouching: how to repair colored blobs

[Ofnuts]

We want a "soft" selection on the reddish dots. These are reddish because their color has more red than blue or green. We can use that  to isolate the spots with the Monochrome mixer:

• Duplicate the layer
  
• Colors>Components>Monochrome mixer
  
• Set the Red multipliers to +2
  
• Set the Blue and Green multipliers to negative values, try to find the combination that makes the spots stand out.
  

   

• To avoid changing other parts of the picture, cover the right part of the picture with black (no need to be very accurate, except along the lady's arm since it touches one of the spots).
  
• Use Levels to make the lightest part completely white (Levels, not Threshold, the selection must remain "soft". The final selection should look like this:
  

   

• Open the Channels list, right click any of the RGB layers, and Channel to selection
  
• Back to the Layers list, hide the B&W layer, and select the initial layer
  
• In Levels or Curves, select the Red channel, and reduce its maximum level
  

   

• Final result: