Tame Out-of-Gamut Colors
Next, choose Select>Color Range, and in the Select menu, choose Out of Gamut, and Click OK to load a selection of the out-of-gamut colors. Then, choose Image>Adjustments>Hue/Saturation and move the Saturation value to -10, and click OK. You should see the gray areas get smaller. Deselect and repeat this procedure using the same -10 Saturation setting until the gray color indicating out-of-gamut colors is no longer visible.
I am sorry – but this doesn’t work . You end up with a virtual B/W image