It’s not neccessary to purchase diffferent colour foundations. The trick is simple: foundation must always match your NECK colour. So test the foundation on the jaw line, blend up onto the face and down onto the neck. If the colour blends well onto the neck then it is the correct colour. For darker areas on your face, you can use a concealer. I would recommend purchasing two different colour foundations only if you cannot seem to find a shade that matches your skin.