Adding A Splash Of Colour Into A Black & White Photo

I have learned how to changed a photo to black and white, and then input a splash of the original colour back into the picture. Firstly, I opened the image I wanted to work with and made a duplicate layer.

I then converted the top duplicate layer to black and white.

I then selected the 'Eraser' tool from the tool bar on the left hand side of the screen, and adjusted the brush size and made it a soft edged brush.

I then used the eraser brush to erase the top black and white layer over the subjects blue jeans and college card, letting the original colour underneath penetrate through.

Until I was left with this final image....