What does it indicate when a lighthouse light changes from white to red as you pass by?

When a lighthouse light changes from white to red as you pass by, it signifies a warning to mariners that they are approaching an area of shoal water or another navigational hazard. The transition from a white light, which typically indicates safe water or navigational assistance, to a red light serves as a crucial alert. This color change is a universally recognized marine signal indicating potential danger and prompts caution.

In maritime navigation, colors have specific meanings; red lights are commonly associated with hazards, while white lights provide information regarding safe passages. Thus, when a vessel observes this color shift, it is essential for the operator to take appropriate action to ensure safety, such as altering course or depth to avoid grounding or encountering dangers in the waterway.