This is quite tricky I have to say, first you have to know what kind of skin type you have or what kind of skin type you are going to apply the foundation on. And then you have to figure out what type of effect that you want by applying the foundation you choose, you want it light and invisible but still a bit matte or you want a full cover, matte but still with a little fresh, healthy skin, type of shine at the same time?
And then you have to color match the foundation with the skin you are applying it on. And not only that, you also want to use the foundation as a neutralizer and/or a freshener to the skin, because sometimes you have this little redness in your skin, or can be yellowness, oliveness or greyness… ehmmm, oh well! I think you get my point. Let’s work with redness for now and lets say you like to choose a very light foundation, say up to 4% pigmentation, thats from like a tinted day cream to a very light fluid foundation, it wont cover much, but it can still neutralize some of the redness in your skin if you choose the right nuance but going towards a little olive tone, which are in simple words, it got some green pigment in it, that will if you know your color wheel/schemes neutralize redness in the skin. And some yellow pigment, to give a little coldish skin tone some warmth. (To make it easy: Green and Yellow= Olive). Then perhaps you need to add a little more warmth or so, that you can do either with adding a little yellow pigmentation to your substance or just use a powder on the end that has that little yellow nuance, but for that type of light foundation I had in this example, you might not want to add any powder in the end, then you just have to add more warmth to your foundation before applying it.
For you who been doing make up for many years, this comes naturally without thinking whiles applying, but for many this is still hard after years working with applying makeup, but to try to explain this and teach it, is very hard because this is complexed, to really see the nuances in the same color takes a lot of training, and to on top of that be able to know what exact pigment/color to add to a foundation when you don’t find the right one in your bag is really tricky sometimes, and if you are a blond, pale skin makeup artist used to work in scandinavia with more of the northern European skin tones and travel to Asia, South America or other continents where you might end up working like Nairobi, Mozambique or South Africa, just as for give you a few examples, you will get into some color matching trouble, questioning yourself why you didn’t spend more time to really learn your color theory, because that’s no different to match a darker skin tone than a lighter if you just know your color theory. Is just colors and nuances. I hope to be able to get you to at least understand it, then you have to go on learning by doing!
Here are a tip on a brand that actually helps the client to know if the foundation is neutral or got a undertone: CARGO