What does your "Add to Cart" button look like? Does it say "add to cart", or something else? What color is it? What’s its shape? How big is it? And does any of this matter? The answer is yes.
Link: Collection of 107 Add to Cart buttons of the Top Online Retailers – Get Elastic Ecommerce Blog.
MarketingSherpa: Shopping Cart Design Tests – Color & Size Lift Results 44.11%
"One office supply retailer wanted real answers, so they tested five specific color and button size design elements. The results didn’t go as expected — one change lifted conversions 44.11%"