Some women still believe that a non yellow based (anything that’s pinky or peachy toned) foundation looks best on them because that’s what they’ve always used. But it doesn’t look good. It looks obvious and will sit on the skin.
Most skins have yellow undertones, so a yellow based foundation will disguise discolorations and disappear into the skin, which is exactly what you want it to do. If you tend to have a lot of redness in your skin, a yellow based foundation is especially important to cut red and bring your skin back to a color-correct tone.
Many cosmetic lines have caught on by now that a yellow based foundation looks best on most people, which is the majority of what you’ll find for department stores brads.
There are always exceptions though, so you need to be armed with information when you go out and find a foundation that’s right for you and ask for something yellow based.