We have two categories of skin-tone, cool tones and warm tones. One way to find out if you're not sure which skin tone you are are by actually looking at your veins. Should your veins be blue, you have a cool skin-tone. Should you have green veins, you have a warm skin tone.
Now that you've determined whether your skin tone is warm or whether your skin tone is cool, it's time to choose a red shade. Now many people just think, "Okay, red. It must all be warm." But actually, that's not the case. Some red hair dyes are actually an orange, copper-based and some red hair dyes are actually a purple base or an auburn base.
If your skin tone is warm, I would generally recommend a hair color that has a golden-copper base. If your skin tone is cool, generally I'd recommend a hair color that has a cool base, such as an auburn or a purple. I don't mean a red that actually looks purple. It's what's inside the red. Just as I don't mean a hair color that is orange, it's what's inside. Whether you have a cool skin tone or a warm skin tone, there is a red color for you.