Does anyone know what happened to the Manilla Folder variation that was in the Leopard betas? Are they still in the Leopard today?

Nick.

Nope they're gone, didn't make it into the final version (at least not in the CoreTypes.bundle where they were during the betas). I never figured out what they were used for in the betas. Maybe something network related?

Yeah I remember those in the beta but I can't say that I like them to be honest.

I prefer the blue, but it's always nice to have options

If you want the manilla ones or a few other colors for that matter check out MoCo design. He released a set called Smooth Leopard which has the exact manilla color you are looking for.

http://susumu.seph.ws/?page_id=11

Those were part of the discontinued Silica replacement for Aqua. It was a modular section of the UI that the UI team decided not use in favor of the Unified iTunes Interface we now see in 10.5. I do not believe it was ever seen in a public version of OS X. (One of those secret features Steve mentioned)

Can you tell us more about this Silica replacement? Maybe even a screenshot?

Yeah any details? First I've ever heard of it.