When setting the color property of a Ti.UI.Label to null it makes the color transparent on Android. On iOS and Mobileweb the color is returned to the default black (#000). While the default color can be determined by the underlying platform, it should be a visible color to give parity across the platforms. In others words, setting color to null should either make the color transparent on all platforms, or a solid color on all platforms.
When I set the the color property of a Ti.UI.Label to null, I expect the behavior, whether it makes the Label transparent or a solid color, to be the same on all platforms.