ArcoLinuxD with i3 is the basis of our distro. Then we look for a wallpapers we like and use its color to get us started. With gpick we find out what hexadecimal code it is and then we use it.
We use atom and its package pigments. Then we start changing the color codes.
We show you the wallpaper selector in i3. It must be the only window open on the workspace in order to move the pictures to the right or left.
Then we change the colors one by one or we change all at once via CTRL + F and replace all.
I do not have all the answers about all these settings but i3wm.org has them.