If you polish the titanium to an extremely high shine, and then anodize the interior at a very low voltage, you can get a highly reflective silver finish - not white, but may better show the colour of the tea.

I wonder if you could then place a weight in the cup (and submerge it, but only to just the brim) to anodize the outside at a higher voltage, which will produce a thicker and more durable coating.