Blizzard added a spark entry for the PowerBarColor.Stagger entry that doesn't have r, g, b entries.
You could try changing line 145 of RuF\Libs\oUF\colors.lua from:
Lua Code:
colors.power[power][index] = oUF:CreateColor(color_.r, color_.g, color_.b)
too:
Lua Code:
colors.power[power][index] = oUF:CreateColor(color_.r or 1, color_.g or 1, color_.b or 1)
Hopefully it doesn't do anything funny elsewhere.
They also changed the color keys for stagger from numbers to strings ("green", "yellow", "red", [and the new "spark"]) so that may also be problematic but the addon is a bit on the large side to just wander through on the off-chance.