Here is a good picture of the color difference of the shingles. They had yet to replace the shingles on the shed (old roof) so I took a picture before they did.
Our roof with new architectural shingles in pewter gray and no roof vents on the front side of the roof. Very happy with our decision!
Thank you again for all your help with this decision. I received a lot of great input that helped us make very informed decisions. If you're considering installing a new roof, you should read comments from readers here and here.