I saw an E46 in titanium silver which had a darker grey hardtop on that looked good, and I'm actually tempted to do it to mine.
I know your thinking why pay extra for a mismatched hardtop but its actually not that difficult for me, I bought it wrapped in matt black vinyl thinking it was titanium silver underneath, I even removed the vinyl off the spoiler and didn't notice the difference straight away as its so far from the car, but realised when I took it off that its actually a sterling grey roof so I could just unwrap for the two tone silver grey look