Yes! I have weird coloring (very pale with olive undertones, but flushed areas of pink) and I have to mix 2 colors (next to each other on the color spectrum) to get a good match. I've tried so many brands and this has been the best solution for me.
Yes, which is funny because I was so against it (damnit, if you want me to buy your foundation I'm not doing the color mixing for you). But I found a foundation I really like, and now I mix. Sometimes either color alone will work, but not very long. It's worth it, and while initially very expensive lasts a really long time....