In 1998, Ralphs was taken over by Fred Meyer, which was itself taken over by Kroger very soon afterwards. The main effect of these ownership changes, it seems, has been to make Ralphs the home of a bewildering array of different store brands: Ralphs brand, FMV and Private Selection (the Fred Meyer downscale and upscale store brands, respectively), Perfect Choice (a Kroger brand), and occasionally, a stray product or two with the Kroger name.
The look of the labels on Ralphs brand products is familiar to people outside their marketing area, because they're often used as props in movies and on TV shows. The labels are black, with bold white lettering, which means they show up on camera much better than Vons brand products. There's also a Ralphs logo which the propmasters usually remember to cover up with a blank red oval.
Update, August 2002: Every time I'm at Ralphs, more and more store brand products that used to be sold under the Ralphs name are now Kroger brand. For example, lsat time, it was strawberry-banana yogurt (all other flavors were still Ralphs), and the time before that, it was cheddar cheese.