This is one of the things that make Meteor a very flexible & powerful theme. The colors are automatically calculated for you, based on predefined sets of styles available in the theme’s stylesheets. You can control how every aspect of the site will look like, by choosing a minimal amount of colors. The theme does the rest by automatically calculating the right contrast based on the colors you have chosen.
Another awesome feature is that you can have Multiple Color Themes. This allows you to have a group of styles, and switch them whenever you please (for example, a Christmas or Autumn theme). If you are working locally, you can then export your color themes to a JSON file, which you can then import into your live site. Awesome huh ?