One way is to take a pattern in a clothing item I already have and pull colours out of it. The other is to copy something I see. The easiest thing for me is to look at nature, especially flowers:
This outfit is a bit of both. The shoes are green, yellow and purple, so duh, that's pretty simple. But I also have a life-long fondness for the flowers that were in the garden of the house I grew up in. I love pansies:Isn't that just gorgeous? You could do purple, white, cream, yellow, fuschia, black and brown - and they'll all go together, because there they are, all in one flower!
As soon as I put this lovely purple shirt next to the shoes, I looked around for some yellow in my wardrobe. I have a lot of pale yellow, but when I held this mustard yellow cami up to the vivid purple, they really popped together:
I was very rattly with the charm bracelet today! Hee! That's a big ring, by the way.
Shirt (H&M, thrifted), cami (Smart Set), skirt (Club Monaco, consignment), shoes (Enzo Angiolini, thrifted), bracelet and necklace (Plum), earrings (vintage), ring (Guess).