Skin tone can be thought of as the surface colour of your skin, determined by the amount of melanin your skin has. You can determine your skin tone by the colour you first see when you look at your skin in the mirror (fair, light, medium, dark, deep, or somewhere in between), and although this can vary slightly throughout the year, most people will know roughly where they fit on this spectrum.
Your undertone is the subtle hue underneath the surface level of your skin (warm, cool or neutral). There are many ways that have developed over the years to determine your undertone, but on the whole, the ‘vein test’ seems to be pretty effective. Look at the veins on the underside of your wrist. If they appear to be blue or purple, you most likely have a cool undertone. If they seem to be green, your undertone is warmer, and if you aren’t sure, you likely have a neutral undertone.