When purchasing a MAC foundation you will notice that each color has letters before the number, NC25 for example. The letters describe the undertone and the numbers tell you how deep the shade is. Although this may seem a little confusing, it is actually very helpful when trying to find your perfect shade.
MAC foundations are one of the following:
N -- Neutral
NC -- Neutral Cool (slightly yellow)
C -- Cool (very yellow)
NW -- Neutral Warm (slightly pink)
W -- Warm (very pink)
I know what you're thinking... "Why the hell are they calling a yellow foundation cool?" In reference to skintones many people think that cool undertones means pink based and warm undertones mean yellow based -- well in the MAC world, reverse that!
According to MAC yellow undertones = cool, and pink undertones = warm. And here's why:
According to Color Theory cool = blue, and warm = red. It only makes sense to say that if you have pink undertones you are much closer to red in the color wheel and therefore warm toned. If you have more yellow/olive undertones then you are closer to blue and therefore cool toned.
I find the pink and yellow undertones in MAC foundations to be quite strong, even in the NC and NW shades! Unfortunately they don't have the neutral (N) shades in many of their foundations.
A couple more points before I wrap it up... Make sure to get matched if you plan on switching foundations. If you are an NC30 in one foundation, you could be NC25 in another! Also, if you have a lot of facial redness like I do, I would suggest trying an NC foundation. Because it is slightly yellow, this will help to counteract the redness and can give a better result.
I know it can seem a little confusing, but hopefully this helped! Thanks for reading!