Hi! I've been thinking this for quite a while, and I know most of the web designers out there have the same need... groupable, colorable, nameable guides.
It's important to use guides. But sometimes it gets a little messy.
What would be perfect is if guides had their own layer-style format. And each group, or layer, had an asigned color. You could turn on and off visibility of specific groups, or just turn them all off by hitting cmd + H, as we do today.
This would make photoshop THE perfect software for web design.