I don't know much about the subject either. When I tried small wire I got a darker blue @ 30 volts in anodiziong electrolyte , and I didn't check the amps. It may have drawn so little ( for a few inches of .06" wire) the the resolution on my power supply would have been too poor to get an idea.
The racks (more surface area) don't anodize the same colors at the same voltage, so maybe the current density is what determines color.
Here's the only Ti anodizing link I found on my computer.
http://mrtitanium.com/anodizing.html