Roy G. Biv

You may pay all costs for an ability on a permanent you control that can add mana of any color rather than pay Roy G. Biv's mana cost.
Roy G. Biv's power and toughness are each equal to your devotion to rainbows. (Each
set of {w}, {u}, {b}, {r}, and {g} counts one towards your devotion to rainbows. Sets can be split between permanents.)