California Code, Vehicle Code - VEH § 9853.4

(a) The department may issue one or more stickers, tabs, or other suitable devices to identify vessels as being currently registered.  The size, shape, and color of the sticker, tab, or other device and the positioning of the sticker, tab, or other device on the vessel shall be as determined by the department after consultation with the Department of Boating and Waterways, such consultation to consider the responsibilities and duties of the Department of Boating and Waterways as prescribed in the Harbors and Navigation Code.

(b) Whenever the department issues a sticker, tab, or other device pursuant to subdivision (a), the sticker, tab, or device shall only be displayed on the vessel for which it was issued.