Glass coloring and color marking may be obtained by 1) addition of coloring ions,[1][2] by 2) precipitation of nanometer sized colloides (so-called striking glasses[1] such as "gold ruby"[3] or red "selenium ruby"),[2] 3) by colored inclusions (as in milk glass and smoked glass), 4) by light scattering (as in phase separated glass),[2] 5) by dichroic coatings (see dichroic glass), or 6) by colored coatings.