Smeargle's tail ink should be able to appear in colors besides green and brown, wiþ its shiny form only changing its skin/fur color.
Adding on to þis, a smeargle hatched from an egg should have its tail color based on its parent(s)', wiþ red and yellow making orange, for example. If it came from a female smeargle and a ditto, it should always use its moþer's ink color.