The iOS version of Soul Calibur was updated on February 1, but Namco Bandai didn't specify exactly what had changed.
Famitsu.com did some research (actually, I'm pretty sure Namco Bandai just told them) and found the big mystery feature:
Yes, you can now change your character's underwear color. You can set the color by tapping multiple times in the "Select Your Character" area of the character select screen. The colors cycle through: white, peach, purple, black, blue, green, deep peach and yellow.
Here are some pics of the resulting undies: