Since the Screen on a PSP is a Liquid Crystal Display (LCD), dead pixels would appear as Black, small tiny dots.
Quick question before continuing: Do these stay in the same place, regardless of what you're doing on the PSP (Playing games, watching movies, browsing the web, ect)?
Pink dots on the other hand does ring a bell to me. While I was doing TV tech support for Comcast, problems would come up where a tv would go all pink, there would be pink dots on the screen, and all things in common with these issues would be the connection (In those cases, HDMI), which I would tell the customer to try a different type of HD input (Component or DVI) and see if it fixed it, or send a tech. But since the PSP is a different beast and the connection is inside the machine, I have to ask: Have you dropped it, or otherwise done anything that would damage the internals of the device, and if not, is it under warranty?