There are two types of colors for rats, agouti and non-agouti. Agouti colors have a ticked hair shaft. In non-agouti colors the hairshaft is the same from base to tip.
A silvered rat has white hairs interspersed throughout the coat. Color should reach to skin. Color standards include: Silver black, Silver blue, Silver Chocolate, Silver Fawn, Silver Lilac, Silver Mink. The rat pictured is an example of silver black.