Just as hair color 101 taught us to balance the hair color choice to complement a client’s skin tone…extensions are no difference. Using your skin can help you find your client's most flattering shade ever. Unless the client wants to make a bold statement and have their hair be the focal point, go for complementary colors.
For skin tones that are warm, choose hair extension shades with a yellow or red base. There are so many pleasant tones within this spectrum, your client is sure to find a tone that suits them. Then, add some dimension with highlights or lowlights.
Cool Skin Tones
For skin tones that are cool, choose hair extension shades with a neutral or blue base. After your choose the base color, you can add some fidelity to your client's hair by doing a secondary color treatment, perhaps a balayage vs ombre effect.