While working on a new site, I started playing around a little more with 8-bit PNG files, comparing them to GIFs. In a few cases the PNG was smaller (it didn’t used to be that way, but perhaps Photoshop CS2 does a better job of compressing PNG files or something), so used it. All was good until I started testing the design in IE, where the colors were all off. Here’s a breakdown of how the same graphic (placed as a CSS background image against a background color equal to its own background color) rendered between the two browsers: 
I am well-aware of the issues regarding IE’s handling of alpha transparency in 24-bit PNGs, but had not heard of any color-related issues with 8-bit PNGs in IE6. I did a test in IE7B2 to see if the error was there too and it was.