My husband just painted our lower underhang , beige to match the house. It was a semi gloss, it had a light sheen.Now he used the flat paint, that he used on the house, and it looks all smuggy to me. Would a second coat help that look ?
Try applying a second coat. Most likely you are seeing some of the background color coming through. Flat paint has a different look than satin or semi-gloss plus it works a bit differently. Adding a paint conditioner, like Floetrol, helps the paint spred evenly and can improve the way it looks.