As this years issue was a bi-color I suspect they ran out of new colors last year(2013), So in developing the means to anodize the niobium pill to produce two colors now gives them many more years of options. As far as I know they have no plans to stop.
I may be wrong in my maths but they produced ten years worth of mono-colored niobium coins.....so that gives them a possibility of 100 different bi-color options. Knowing the Vienna mint next years will be a tri-color