A colleague of mine just picked up a 16 GB iPhone 4 in white.

I was a bit surprised when I picked it up off his desk (I had my black 32 GB in my other hand at the same time) – it immediately felt thicker.

We placed them side-by-side on his desk, and sure enough, the white iPhone was a hair thicker.

Apple doesn’t list any sizing differences on their Tech Specs page for iPhone.

I’ve already heard from a few people that their previous iPhone 4 case won’t fit on the white one – this could become a huge issue if it affects a lot of users. My guess is it won’t, as most cases aren’t extremely tight-fitting.

* Updated with pics *

It’s a little hard to tell from the photos, but it’s the plastic white glass part (not the aluminum stainless steel) that’s thicker.