Firstly take off your make up (not right now obviously unless you're alone!) and pop on a white t-shirt or shirt. Now stand in front of the mirror and have a look at your skin tone. It will either be reddish, yellow, or pinky-blue. If it is more towards the red / yellow then you have a warm skin tone, if it's pink-blue then you have a cooler skin tone. Another way is to look at the underneath of your forearm. What colour are the veins? If they are a blue colour then you have a cool skin tone, a warm skin tone will give you greenish veins. If you still can't decide, the final trick... Gold & Silver Jewellery. Pop one on, which one pops out most against your skin tone? Silver means you have a cool skin tone, and if the Gold is more prominent, then you have a warm skin tone. This helps when deciding what type of hair colour to choose!
Here we are recommending shades of natural colours, have a look at your own hair colour and tone. Stay around versions of this.
So if you are warm, look at warm blondes, browns, reddish caramels and coppers.
Cool skin tones look better in colors like ash or wheat blond, coffee brown and deeper auburn reds. Neutral skin tones will look good in almost any shade.