Ignis fatuus

"I'm seeing a rainbow!" Laura shouted. Her friends looked at her, suspicious. "Are you sure?" Alice asked dubiously.

"Yes yes! I can see it!" Laura said. Christy raised her eyebrows. "That is so odd." she mumbled. "Don't mumble." Alice said absentmindedly.

"Are you sure you can see a rainbow?" Kimmy asked. Laura nodded vigorously. "Yes yes! I can see it! When I sit in this spot, in this angle, I can see a rainbow. The colours are so pretty!"

Laura frowned. "Why don't you believe me?"

Kimmy, Alice and Christy looked at Laura in amazement.

"Because you're colour-blind."