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A: Matt Tabak, Magic rules manager:
When counting your devotion to either a single color or a pair of colors, each mana symbol counts only once. A hybrid mana symbol is the color(s) of its component parts. So, for example, if you control just a Azor's Elocutors, your devotion to white is two, your devotion to blue is two, and your devotion to white and blue is two. If you control just a Reaper King, your devotion to any one color is one and your devotion to any pair of colors is two. If you control Azor's Elocutors and Ephara, God of the Polis, your devotion to white and blue is four (and Ephara isn't a creature… yet!).
Another way to think about it is if you're calculating your devotion to white and blue, for each mana symbol among the mana costs of permanents you control, ask yourself, "Is this mana symbol white and/or blue?" If the answer is yes, add one to your devotion.