Answer the following question given this paragraph: "Neon" signs are familiar examples of gas discharge tubes. However, only signs that glow with the red-orange color seen in the figure are actually filled with neon. Signs of other colors contain different gases or mixtures of gases. Q: What colors in a neon sign represent real neon? A:

OPTIONS:
- purple, blue.
- blue, green.
- yellow, white.
- red, orange.
The answer is:
red, orange