If the veins are predominantly blue-purple, you’ve got cool undertones. If they’re mainly green, you’ve got warm undertones, and if they’re a mix between the two, you have neutral undertones.
For example, if you have golden skin, then an ivory blonde or an ash or mocha brown would look great on you. If you have cool skin, then a copper red, golden blonde, or honey brown would look great on you. If you have a neutral skin tone, then you will look best in muted shades, such as mahogany.
If you have a warm, golden undertone and a lighter shade of dark skin, you can really choose most any hair color, from light to dark browns or reds and blondes. Highlights that contain a red base can help accent golden undertones.
For example, if you have cool, pale skin, then opt for warm colors, such as golden browns and copper reds. If you have tan skin, then opt for cooler hair colors, such as ash browns and blondes.
If you choose a blonde base or blonde highlights, you may end up overemphasizing your yellow undertone.
Choose burgundy, cherry, or garnet hair color for dark skin with cool undertones. You can use these as a base color or highlight color. The cool red tones in this hair color give your skin a smooth even look.
If doing highlights, try a warm red color to really bring out the warmth of your skin tone.
If you have dark olive skin with cool undertones, avoid choosing a light ashy blonde or something similar that will starkly contrast.
