4 Ways to Convert Colour to Monochrome

1. Go to "Image", then "Mode" and then "Grayscale". This converts RGB to Grayscale.
2. Go to "Image", then "Adjustment" and then "Desaturate". This method removes colour information.
3. Go to "Layer", then "New Adjustment Layer" and then "Channel Mixer". adjust the colours like so: Red = 40%, Green = 40% and Blue = 20%
4. Go to "Image", then "Adjustments" and then "Hue/Saturation". Change the Saturation to -100%
Whatever way you use, you will always end up with a black and white picture like this: