Bakemeacookie shows a new one in his, but the old ones (pre-1990s issue) were like what you're saying. About 4" x 3", and pink on the front with the CA state seal in white, and white on the back. It should be fine. If in doubt, go to the DMV in whatever state you're going to register the car in, and have them run it and tell you what papers you need. If the pink slip is no good/off file, you might have to apply for a new one, which just means having a law enforcement agency look at the VIN number on the car, and certify that you wrote it correctly on the new application. I do that all the time with my weird old Diesel car collection. The new type title is still nicknamed "pink slip", but they're larger (9 x 9 or so), and are a rainbow of colors like a bond certificate.
Charles