White. The background color of digital image retrieval on library homepage is usually white. Digital image retrieval is an online retrieval service provided by the library. Users can query the collection resources by inputting keywords or constructing retrieval formulas. The library homepage is the entrance to provide this service, and the background color is usually set to increase the visual effect. As a common background color, white can highlight the search box and search results, making the whole page look more concise and clear.