A color theme is a package that sets a ton of faces and variables for you. This page collects reviews and recommendations of the various colour themes out there.

These are all implemented using custom themes.

(There is a separate color-theme.el package, which installs color themes by modifying Emacs faces directly instead of using the custom theme (Customize) framework. It hasn’t been updated since 2009, and now it is more common to use custom theme. See comparing color theme and custom theme for a comparison of the two.)