For anyone not aware of this mighty application and simultaneously struggling with defining color themes:
STRUGGLE NO MORE!

https://kuler.adobe.com/#create/fromacolor

Choose a base color and a rule and create your own color-theme.

From Adobe's About page:
Discover Adobe® Kuler® — the web-hosted application for generating color themes that can inspire any project. No matter what you're creating, with Kuler you can experiment quickly with color variations and browse thousands of themes from the Kuler community.