These are the Blizzard color codes for power bars of various types. You can determine the power type with UnitPowerType(unit).

["MANA"]        = { r = 0.00, g = 0.00, b = 1.00 }
["RAGE"]        = { r = 1.00, g = 0.00, b = 0.00 }
["FOCUS"]       = { r = 1.00, g = 0.50, b = 0.25 }
["ENERGY"]      = { r = 1.00, g = 1.00, b = 0.00 }
["HAPPINESS"]   = { r = 0.00, g = 1.00, b = 1.00 }
["RUNES"]       = { r = 0.50, g = 0.50, b = 0.50 }
["RUNIC_POWER"] = { r = 0.00, g = 0.82, b = 1.00 }
-- vehicle colors
["AMMOSLOT"]    = { r = 0.80, g = 0.60, b = 0.00 }
["FUEL"]        = { r = 0.00, g = 0.55, b = 0.50 }