From CA's DMV site: http://www.dmv.ca.gov/pubs/plates/licenseplthistory.htm
Basic information on 1963- present plates:
1963 was the last year a complete new plate issuance to all vehicles occured (the plates had a black background and chrome yellow characters).
1970 is the year the basic plate was changed to a blue background with yellow characters. It was also the last year any black/yellow plates were issued.
1976, year round registration started which requires a month expiration sticker afixed to the upper left hand corner of the plate.
1982 is the year when the standard plate was changed to a white background with blue characters with a sun graphic and CALIFORNIA in red block letters. It was also the last year any blue/yellow plates were issued.
1987, reflectorized plates with CALIFORNIA in red block letters were issued. The sun graphic was discontinued.
1991, only reflectorized basic plates were issued.
1993, the word CALIFORNIA was changed to red script.
1997, stickers were made with background colors that change every year and characters printed in black.
Basic plates issued from 1998 through 2000 contain the words SESQUICENTENNIAL - 150 YEARS in red block letters at the bottom of the plates.
2001, the basic plate is white with blue characters and CALIFORNIA in red script. There is no writing at the bottom of the plate.