Final answer:
The green-colored appearance of glass is primarily due to the presence of iron(II) oxide and chromium(III) oxide, which reflect green light. This is a principle also seen in the natural world, such as with green leaves reflecting green light and is exploited in stained-glass art where various oxide additives are used.
Step-by-step explanation:
The main reason the glass appears green is due to the presence of certain oxide additives in the glass. Different oxides produce different colors when added to glass during its manufacturing. For example, iron(II) oxide and chromium(III) oxide lend a green color to the glass. These oxides absorb some wavelengths of light while reflecting others, and in the case of green glass, the reflected light is predominantly in the green spectrum.
This principle is similar to why leaves appear green; the molecules within them absorb all visible light except for green, which is strongly reflected. Artisans have used this knowledge of color and color vision to create stained-glass artwork for over a millennium, commonly utilizing materials like silica and various oxide additives.
In advanced glassmaking, such as for the creation of a memorial window depicting magnolias and irises, different colored glasses including opalescent drapery glass were used without the need for painting before firing, allowing the glass to exhibit its inherent colors based on the materials used in its creation.