Isolating similar colours when making a selection

When the colours are too similar to be easily distinguished from one another by the magic wand tool (especially when using the default settings that were used for the black and white image) you will notice that the whole area will be selected instead, as shown below. To remove the selection go to select > deselect....

Play with the tolerance levels on the menu bar and you will notice that you have to take the setting relatively low in order for the magic wand to determine the colour that you want to select. 30 is often a comfortable setting, but if the colours were even more similar than these used in the example, then you may have to go a lot lower.