Will the inside of properly closing expansion joints be light or dark in color?

The correct answer is that the inside of properly closing expansion joints will typically be light in color. This is primarily due to the materials used and the design intent of these joints. Many expansion joints are constructed from materials such as rubber or various polymers that tend to be light-colored.

When these joints are properly maintained and closed, they promote good flow and minimal wear, which contributes to the maintenance of a lighter appearance on the inside surfaces. Additionally, the presence of any build-up or corrosion may indicate issues with the joint's operation, which would not be the case if the joint is functioning properly.

While it is possible for the color of expansion joints to vary based on different factors, including the specific material used or any degradation over time, generally, a well-functioning expansion joint will present a lighter internal surface.