This tutorial will show you how you can turn an image to black and white and keep a single colour range in colour. In my example the colour kept in the image will be the red of a London bus, but this process can be used with any colour on any image.
When you have opened up the image in Photoshop. The layers palette should look similar to the below. (F7 opens the layers palette).
Duplicate the background layer. (Ctrl J / Apple J)
Select the background layer in the layers palette and desaturate the image (Image > Adjustments > Desaturate / Shift + Apple + U / Shift + Ctrl + U).
If you toggle the eye icon on the top layer in the layers palette you will see that the image on the canvas has been desaturated as shown below:
Turn the top layer back on and select the top layer this time. Bring up the Colour Range options (Select > Colour Range…)
Choose the eye dropper on the Colour Range Panel and click on an area of colour on the canvas that you want to keep from the photograph. In my case I clicked on the red area of the bus. To see clearly the colour range you have selected change the ‘Selection Preview’ at the bottom of the colour range panel to ‘white matte’.
Below is an example of what the canvas looks like with the above option toggled.
Use the other eye droppers on the Colour Range panel with the plus and minus to select and deselect more areas on the canvas until you are happy that you have all the coloured areas selected that you want.
I used the eye dropper with the plus to continue selecting the red areas by clicking on any areas of red that looked a little patchy.
If you select too much you can use the eyedropper with the minus to deselect any areas you don’t want to include.
Below is the red areas all selected that I was left with.
When you are happy with the selection choose ‘OK’ and you will see everything selected on the canvas as below.
Since we need to delete everything that is not in the selection we need to inverse the selection. (Select > Inverse / Shift + Apple + I / Shift + Ctrl + I)
Now all you need to do is hit the delete key to remove the colour that you don’t want. Then deselect the dotted lines (Select > Deselect / Apple D / Ctrl D)
The layers palette will now look similar to the below.
The below is very close to the image that I wanted to produce but I only wanted the red of the bus. In my image there are a few other areas such as the red on the taxi that I don’t want included.
To remove any extra areas simply select the eraser from the toolbar.
And with the top layer still selected in the layers palette erase the areas that you don’t want with an appropriate sized brush.
Below is my final image
I hope you enjoyed the above tutorial. If you have any questions on the above please use the comments below.