A tag similar to [raidcolor] but for power color (eg if Warrior then set FontColor to RGB 255, 0, 0)

Will help out rookies such as myself that can't grasp the PostUpdate Function quite yet.

You can easily add this tag yourself:

oUF.Tags.Events['powercolor'] = 'UNIT_DISPLAYPOWER'
oUF.Tags.Methods['powercolor'] = function(unit)
    local _, powerType = UnitPowerType(unit)
    return Hex(_COLORS.power[powerType] or _COLORS.power.MANA)
end

Such a simple (and most likely commonly used) tag should be implemented into oUF itself though.