Color depth statistics in Awstats
Just add the following lines in your awstats.XXX.conf file, near the part where you configure the extra sections:
ExtraSectionFirstColumnTitle1="Color depth in bits"
In a common-person oriented website I manage (as opposed to techies), 75% have 32 bit depth, 18% have 16 bit, 5% have 24 bit and 2% have just 8 bit (that's 256 colors). I'll have to use my screen in 16 bit mode once, so as to check how things look.