The Magic Wand tool selects similarly-coloured pixels, for example the red pixels in an image of a red car. The tool's tolerance setting controls range of pixels it selects.
With the Magic Wand tool selected, enter a value from 0 to 255 for Tolerance.
A low tolerance selects a few very similar colours to the pixel you click. A high tolerance selects a wider range of colours.
In the Options bar, turn anti-aliasing on for a selection with slightly softer edges or off for hard edges.
In the Options bar select Contiguous to select only adjacent pixels of a similar colour. If Contiguous is not selected, all pixels with the same colour throughout the image will be selected.
Select Use All Layers to select colours from all the visible layers. If this is not selected, the Magic Wand tool will selects colours from only the active layer.
Click on pixels with the colour you want to select.