Site Colors Under Design?

Hello all. I'm curious what these colors represent when I set them? There's no label to each color I set to indicate what will change with the color choice in slots 1 through 5 (as seen in the image). 

This is all under the Design feature once you get into the Website Builder online. 

I'd love to know what slot to put which of my site theme colors in, if that means it will make the things I do more automatic.  Any ideas?