With the passage of time the color tone of the metal house number plaque may get lighter. This is due to fact that the metal plaque is exposed to weather conditions that are not the same throughout the year. Sometimes there are extensive sunlights and sometimes there is heavy rainfall around the year. Due to heat the metal may lose its color and get lighter. In that case you need to revive the originality of the metal. One of the common way is to use some sort of the paint. The paint will get the metal house number plaque looks darker.