Ever consider a slate grey or plum colored door?

There are a wide variety of doors to choose from in the style that you seek. Since this is a covered porch you seem to have options for what material to choose; wood, fiberglass, or steel. The material will affect the price. I think with the dog scratching you would be better to select a manufactured material. Most doors come in standard colors so you would have to have it painted the color of your choice unless you are going custom. A dark blue or blueish gray could be a nice color option with your yellow house. You can play around with this website to see door options available in the style you seek: http://www.jeld-wen.com/catalog/exterior-doors.