I've seen them both. Some have red bottoms, some have white bottoms.
I had to look at one that was perfect in every way, but the lady who bought it thought she was getting a red bottom and refused to accept the white bottom claiming that the board had been repaired or was a 2nd and had been refinished at the factory.
Hey, ALL Starboards are pretty much "handmade/hand finished" so I do not think we will ever see the consistency of truly mass produced/robotic QA inspected products.
Some come out of the factory a little more "perfect in every way" than others, but I've found that the vast majority sail identically.
Perhaps ask Tiesda if he can I.D. (by serial number or date of mfg.) which have white paint on the bottom and which have red paint on the bottom.
Hope this helps,