One more thing about combining color:
I mentioned that colors in the same families pretty much always go. That isn't to say that it is *only* colors in the same family. In reality, almost any 2 colors can be combined. There are truly very few colors that clash enough not to work.
However, the less similar the colors, the more difficult. In my example I mentioned yellow cardi and purple dress. If they are both pastels, that is 100% all you need in the outfit. However, if it is a pastel yellow cardi and a deep purple dress, the outfit is going to look better if you then have a yellow necklace hanging in the middle of that expanse of purple (or a yellow scarf), maybe yellow shoes, and/or other yellow accessories. Also, the more neutral the shoe (assuming you don't have yellow), the better, and in this case, a flesh colored ballet flat is going to be less harsh than a black shoe.
So, I find it helps to own scarves, necklaces, bracelets, belts, shoes, or other accessories in the colors of my secondary pieces. (Thats how I think of things like cardigans or blazers, tights, and even sometimes skirts or pants--secondary pieces). That way, you grab the secondary piece and the coordinating accessory, and suddenly a couple disparate pieces become an outfit. Purple dress, yellow cardigan and yellow necklace. Teal top, rich pink skirt, and a rich pink scarf. Cobalt dress, turquoise tights (or shoes) and a turquoise belt or blazer.