Take a look at your sales page, your opt-in box or anything where you are trying to get a conversion.
What is the dominant color on that page?
Whatever it is, choose a CONTRASTING color for your button to increase conversions.
For example, if your sales page is predominately white and green, choose red for your “Add to Cart” button.
If your opt in box is predominately white and blue, choose orange for your “Send My Free Report” button.
The more you can contrast your call to action buttons with the rest of the page, the higher your conversions will tend to be.
Make your buttons stand out as much as a pink elephant in your kitchen.
Test after test shows this is the way to higher conversions, but then again only one test counts: The test you perform on your own site.