What is the color of chlorine gas?

• A. Green
• B. Pale yellow
• C. Orange
• D. Red-Brown

Answer: (A)

Gases get their color from the wavelengths of light they transmit and absorb. Chlorine gas has a distinctive yellow‑green tint because it absorbs some red light and lets the green–yellow part of the spectrum through. In most lab contexts it’s described as green (sometimes noted as greenish‑yellow). So that green appearance is the best match for chlorine gas. The other colors listed don’t fit what chlorine typically looks like, since orange or red‑brown would describe different gases, and pale yellow would be a lighter shade than what chlorine usually shows at standard concentrations. Keep in mind the shade can vary a bit with concentration, but green is the standard description to remember.