Which of the following apparent colors of stars indicates the coolest temperature?

The apparent color of a star indicates its surface temperature, with cooler stars appearing more red and hotter stars appearing more blue.

In this context, orange-red is associated with lower temperatures compared to the other colors listed. Stars that emit light in the orange-red spectrum have surface temperatures below those of yellow or white stars. The temperature scale for stars typically places blue stars at the highest temperatures, followed by white, yellow, and then orange-red stars, which are the coolest in this scenario.

Therefore, the option indicating the apparent color of stars that corresponds to the lowest temperature is indeed orange-red. This aligns with the concept of stellar classification, where color can be used as an effective indicator of a star's temperature and, by extension, its life stage and composition.