Paper is a little, minimal emacs theme that is meant to be simple and consistent. It was first intended to resemble the look of paper, but has diverged from that objective. Still, though, I keep calling it Paper, as I like that name. Paper uses a small colour palette over all the elements. Org headings are specially treated with a palette of equidistant colours. The colours and heading font sizes are calculated using base and factor values which can be edited. See source. It's most adapted for ELisp-Org users, as I'm one such user, though it works fine with Markdown, Textile, Python, JavaScript, Html, Diff, Magit, etc.