Well, as a former art student I have a good grasp of what you might consider classical color theory and actually had someone give me one of those updated "color me beautiful" books. At the same time, I do take a lot of my color-mixing cues from nature. I used to take Christmas card photos for families when the leaves were changing and indeed the yellows made a beautiful "neutral" backdrop that didn't detract from the subject of the photograph, the family's children. I think this can apply to using a yellow accessory. Depending on what it is, the yellow can be worn with almost anything, like a neutral, and doesn't draw all the attention similar to the leaves. It can add depth and interest without subtracting or distracting from the overall look. Where I live you can have blue/purple mountains next to a turquoise sky, and a pink/red dirt and it works. Not a neutral to be seen. Therefore, it can definitely work in an outfit (although it might not work for someone with certain coloring). At the same time, I can drive and hour or two and see redish purple hills mixed with yellow soils and a more true powder blue sky. Once again, lots of combos, no neutrals in the conventional sense, but other colors working as neutrals.
On the other hand, a cool red is a cool red and a warm red is a warm red. Doesn't mean you can't combine a cool red with a warm purple, or visa versa--- but not all reds are cool! If so, I would look rather crummy in red-- which isn't true. I think "color me beautiful" has some nice combinations, and is a good place to start for colors that look good on you. However, it IS limiting. I can successfully wear many colors and combos that aren't recommended for me in those books.
I think classical (as in art) color theory and how well you obey whatever rules set forth by art and fashion depends on what look you want to achieve. You can use the principles of this knowledge to create a look that suits both you and a mood. If you want to look soothing, you can use information about how ceartain colors are muted because they have a higher level of black mixed in. To continue along the soothing path, you may want to pick similarly greyed neutrals, or other colors close to your first color on the color wheel, instead of their compliments-- which will make both colors stand out. A greyed pair of yellow shoes (like Kari's Fidjis) can work without being the focus of an outfit. When they are paired with a pumkin cardigan they are analogous colors (next to each other on the wheel, blend well). The pumkin cardi is also greyed. Now when she pairs the yellow shoes with a grey top, the shoes have more impact, but they still can work as a "neutral" because both of the shades are more muted than a primary color.
My pet peeves are when fashion sites and books limit women on what colors and combos they can wear, not based on skin tone and hair color, but based on things like age. There are plenty of older women whose complexions don't support a hot pink well anymore, but many fashion sites tell women over a certain age not to wear it because it looks like they are trying too hard or is childish. That isn't true, but it may discourage the 40-something Latina woman from trying a very age appropriate style in a color that she could look smashing in.
