:::(1) I do not know why, because I did not follow closely the discussion about it, but it seems to me (according to my memory) that Noetica might know.  (2) For me, brown might have been neither better nor worse than green.  (I was able to read the guidelines satisfactorily before the template was implemented, but I am not bothered by its use.)  (3) For me, the color coding in the solutions in your tutorials is not a problem.