Foundation, Powder, Concealer, Blush, Bronzer,
the speech on the foundation is long and complex. Definitely get your undertone is a useful thing, because you can buy with more confidence the foundation (especially the mineral) and find more satisfaction even tones that harmonize best woman's face.
This is not, however, something quite fundamental, Self-awareness of the woman and possibly the advice of an expert can make foundation and locate the right tones even without a precise identification of the undertone. In the confusion between the nuances of cold and warm, the variety of products available only multiplies the doubts of those who for their own welfare instead is looking for answers.
The reference to manufacturers to ensure product quality and expert advice are the best means to ensure women's certainty of their innate beauty.