1. Open the image with Adobe PhotoShop
2. Unlock the layer (background) by pressing the lock icon
3. Make the background layer black and white by adding a new adjustment layer either by navigating to Layer > New Adjustment Layer > Hue/Saturation... > OK or pressing Command/Control + U (which can also be done by navigating to Image > Adjustments > Hue/Saturation...)
4. In the new pop-up, drag the Saturation slider all the way to the left, -100
5. Create a new layer by pressing Command/Control + Shift + N or navigate to Layer > New > Layer... > OK
6. Add the Light Purple (#682ACD) as the foreground color by double pressing the left of the two color squares, and entering the Light Purple color code. Press OK when done
7. Fill the new layer with the Light Purple color by filling it in with the paint bucket tool (G)
8. Set the new Light Purple layer mode to “Color” and its opacity to 20% in the Layers panel which can be found in Windows > Layers (f7)