Glass is a little incorrect in DF.
Window glass (aka "clear glass") is not made from sand and pearlash.
It is made from sand and a clarifying mineral. In the case of window glass, this is usually calcium carbonate. Alternatives include selenium, and manganese oxide.
All the pearlash would do is help with the melt.
In addition to green, and clear glasses, other noteworthy glass formulations that have bee available since antiquity are blue, red, yellow, brown, purple, and orange. Some being vastly more toxic than others.
For instance, red glass was extrmemely expensive, because it is made with fumed gold as the colorant. It is however, quite dinnerware safe.
Orange is flat out toxic, being made from cadmium sulfide.
Yellow has many possible sources, the best being selenium and cadmium.
Green has 2 flavors: iron, the most common impurity that makes green bottleglass green, and chromium, which produces a very intense, powerful emerald green.
Blue can come as "aqua" type, made from copper oxide impurity, or "ultramarine", made from cobalt oxide.
Purple comes from manganese.
Brown comes from iron in an oxidation environment. (Green from reduction.)
The most common clarifier used to decolorize window glass in the roman up to the victorian era was manganese. In trace amounts the manganese forms colorless complexes with the trace iron impurities commonly found in sand, removing the green color. Depending on the degree of iron contamination, potentially large amounts of manganese are needed. This distinctive formulation of glass turns purple under exposure to UV light, such as sunlight, very very slowly over the course of many decades. Selenium is more forgiving, and turns a dull straw yellow to dingy light brown instead when large quantities are present.
Creation of opaque glasses requires antimony trioxide, or some other opacifier.
Given the supplies available in df, the following colors of glass should be available:
Iron green (bottle glass)
Ultramarine blue (cobaltite)
Deep red (gold fume)
Aqua blue (copper)
Brown (iron, oxidation env.)
Clear (with flux stone)
Glow in the dark "vaseline" (uranium from pitchblende)
However, I doubt that toady will risk even more bugs in the glassmaking system by creating all those variants.