Step 1: Adjust tones for contrast
Activate the Channel Mixer adjustment layer, with Monochrome activated. Set a layer blending mode to Soft Light at 30% Opacity. To adjust the brightness of facial T-zones create a new layer, filling with a solid #808080 grey. Set the layer blending mode to Soft Light, 20% Opacity and use a 15% Opacity white brush to raise highlights.
Step 2: Utilise Channels
Apply a Curves adjustment layer, blending mode set to Color at 50% Opacity and tweak the Curves channels. Also brighten the image with an additional S-curve layer. Two separate Selective Color adjustment layers were added to introduce purple casts in shadowed areas, tweaking Magenta and Blue color drop options.
Step 3: Finalise colours and tones
To add the final details to the image, tweak the Selective Color Black sliders until the amount of purple tonality is correct. This adjustment layer should stay at 100% Normal blending mode at all times. In the same adjustment layers, set the Yellow sliders to 10, enriching Magenta colouring.