As above, you sure its Ti? I think you can try with magnet, Ti has slight bit of magnetism but nothing like that of steel/cromo. My old Raleigh Dynatechs and M-Trax I have all have their Ti tubes painted... I never really understood why but i'm sure I read its because it was a cheap Ti Tubeset and you could see the seam joints in them and made them look 'ugly' unless painted.
It's not that unusual to paint Titanium frames. The most notable manufacturer to do that is Serotta. Sometimes the customers like some color... usually the rear seat-stays are left bare titanium.