I had my colors *done* back in the '80s when it was all the range. A friend with similar coloring had hers done at the same place so it was interesting to compare afterwards. At that time, my hair was brownish black and her hair was closer to a bluish black. Thus, I was told I could wear flat black, and she was told she could wear deep black and a lot of cooler blues and purples than I can. We are both of East Asian descent and aren't particularly fair so probably have gold undertones -- not really yellow but not terribly olive either.
I generally have and had a decent sense of what colors flatter me, but it's the more subtle neutrals that tend to stump me and led me to the color analysis. I wanted to know which beiges work for me since most do not. I also took in my husband to have his colors done since his coloring is so different from mine. He wouldn't have a shred of clothing to his name if I didn't shop for him, but I would be at a loss if I didn't have this aid since he doesn't have the shopping patience to try on more than a few items at a time.
My husband's was done by John Kitchener at Personal Style Counselors, and apparently he is still in the same business after 30 years, and mine was by a colleague of his at PSC. They also divided colors into Dramatics, Understated, Neutrals, Reds, and Eye Colors -- for a particular individual. It helped to learn that certain jewel colors are neutrals on me, which means that I can wear them but they don't provide a lot of energy which is why a solid burgundy or deep emerald dress would be oddly *off* on me.
Color analysis worked for me, but I think I was lucky.