Have a look at a cool free tool for Substance by Vincent Coupal.
1. Pick a Color
Using one of three color systems, pick a color using the Hue and Mix controls, directly from the 2D view.
2. Choose a Color Harmony
Choose one of five different color harmonies to go with your base color and complete the color scheme.
3. See the Results
The colors making up you harmony will be output to a “gradient palette” that allows you to neatly preview the results. You can then quickly tweak and explore different settings/values. The colors making up your color scheme will also be output individually so they can easily be used in your graph directly.