Ryan Deiss and Perry Belcher's "Magic Button"

That's not my test, that's Ryan Deiss and Perry Belcher talking about their "43 Split Tests" product.

The spec of the "Magic button":

Size: 400px wide
Button color: FEB500 Orange
Text color: 000066 Navy Blue
Background (with [payment options logos): FFFFCD
Text: "Add to Cart"

Ryan observed 200-300% increase in sales compared to other colors and text.
Additionally, he noticed 18% bump in conversions for crossed out larger non-sale price.

Read more and see details on his blog at http://drivingtraffic.com/magic-buy-button/

Here is the actual product page for "43 Split Tests" and "Total Access Club" with more hints. As usual lately, the product is free as long as you join the monthly program - the club.