blue The key information is that Sarah's car is the same color as the sky on a clear day, and it's stated that the sky is not green on a clear day. The only other color mentioned is blue (John's car), so by process of elimination and based on the comparison to the clear blue sky, Sarah's car must be blue as well. Let me know if you need any clarification or have additional questions! I'm happy to explain my reasoning in more depth if desired.