Photoshop’s Background Eraser tool can be used to delete a colour of your choice
Using the Eyedropper tool (I) pick out the colour in your image that you want to remove or change.
Hit X to swap the Foreground and Background colour swatches, and select the Background Eraser tool.
In the Options bar set Sampling to Background Swatch, Limits to Contiguous and Tolerance to 40%.
Paint over the chosen colour. You can add a new layer fill with a different colour to the base of Layers palette, which will show through the erased areas.
Another way in which the tool is handy is shown in our blog post about the Background Eraser tool.