This really belongs back at the contractor. If he promised that he could match the staining, then it's up to him to make the situation right. Anytime you're working with dyes, paints, or stains matching colors is always difficult, especially if the old stain was more than a few years old or is no longer made and the existing woodwork had wear to factor in as well. Dyes/paints/stains are known for being different between lots. Merriam Webster Online defines damage as loss or harm resulting from injury to person, property, or reputation. This circles around on itself as injury is defined as an act that damages or hurts. The woodwork is the wrong color, but it isn't really damaged. Therefore restaining to get the color to match is not covered; there is no loss that precipitated the original restaining, it's just something cosmetic the insureds decided to do. This is faulty workmanship and as such is excluded.