- Go to Channels. CMD + Click on the RGB Channel which selects the highlights. Use CTRL + J to copy the highlights onto a new layer. Change the Blending Mode of this layer to Multiply to darken the area. You can duplicate the layer to increase the effect. You may need a Hue/Saturation layer to reduce saturation in a colour image to match a colour. (Video).
Using the Spot Healing and Patch Tools
- 3 Ways to Remove Hot Spots, Highlights or Shine from Portraits in Photoshop - Video by PiXimperfect
Using Shadows & Highlights
- The most accurate way to edit highlights is using Shadows & Highlights (Menu> Image> Adjustments > Shadows & Highlights), however this is destructive and there is not an Adjustment Layer which does the same thing non destructively. However, you can convert the image to a Smart Object and apply this as a Smart Filter.