A good trick for finding the right shade of base makeup (foundation, tinted moisturizer, etc.) is to match it to the skin tone on your neck. You can also use the back of your hand if you're consistent about wearing sunscreen on your face and are fairer skinned there than the rest of your body. Leave the product on for a few minutes to see how it adjusts as it is absorbed into your skin. Note that your shades will likely change seasonally with your sun exposure.