I've used green-gray mats on thousands of pictures. Warm and cool variants of this useful color form the overall background tones of many paintings, possibly because flesh tones contain red; and red is the color wheel opposite, or complement, of green.
How to contact Amazon by phone. The easiest way to contact Amazon's customer service department is by using their toll-free phone number at 1-888-280-4331.
Ultimately, amazon web services has a 24/7 phone number, but only for paying Enterprise level clients. You can see this in their premium support options here. As far part of the Amazon family of products, amazon web services falls under the umbrella of primarily automated support for customer service.