Every 12-tone swatchbook from True Colour Australia has a strip of color combinations (right before the strip telling you not to wash it, and whether you can wear gold or silver jewelry.) Clients unfailingly ask me about this strip, and usually, I bumble along and say something like, "It helps give you a jumping-off point for combining your colors. Think outside the box, it doesn't have to be pants-belt-shirt, it can be pants-shirt-lipstick, etc."
Until very recently, I wasn't a big fan of that combination strip. I rarely used it when harmonizing, preferring to spread out the entire fan and hide the "matching" colors. I didn't love a couple of the combinations. Excuses, excuses.
The real problem: my seasonal wardrobe was too limited for that strip to be any use to me. Before I could combine my colors in interesting and multifaceted ways, I had to actually possess those colors. So, with a rather pitiful working wardrobe, I fell back on my staple combos: Jeans + Colored Shirt. Jeans + Colored Tank + Colored Shirt. Jeans + Colored Shirt + Necklace. And the occasional very fancy Colored Dress.
Don't picture a giant walk-in closet of Dark Autumn glory: my wardrobe is still very small. The beauty of it is that every piece is carefully-chosen, well-harmonized, and (for the most part) high quality. Sure, I have $9 tank tops from Target like anybody else. But I've slowly and deliberately weeded out the "fine for now" items from my wardrobe, and suddenly I'm a kid in a candy store. I can wear anything I want! With anything else I want! And it will look awesome!
Recent 5-minute outfit example: Cognac Shoes + Chocolate Skirt + Olive Tank + Teal Blouse + Red Belt + Gold Earrings + Cognac Purse + Multicolored gemstone necklace bringing in mustard, teal, olive, red.
There was no science or artistic vision to bringing those colors together. It happened very naturally, pulling items from my closet as I was getting dressed. Looking at my Dark Autumn fan right now, I can move the strips around somewhat and put those colors next to one another and see how they look. And I can look at the color combination strip and see that the warmer Dark Autumn colors are not always paired with the warmer Dark Autumn colors. You can do that, absolutely. But the neutral seasons also look very interesting when the warmer and cooler colors are combined. If this gives you the shivers, you can try wearing your warmer-side clothing with cooler-side jewelry to start out, etc. The combination strips often do a good job of showing the warm/cool mix.
I've photographed a combination strip from each parent season, and created coordinating collages.