Is cooler Rigel or Mira

Cooler can be subjective depending on the context, but in terms of stellar characteristics, Rigel is generally considered "cooler" than Mira. Rigel is a blue supergiant star with a surface temperature of about 11,000 K, making it one of the hottest stars visible to the naked eye. In contrast, Mira is a red giant star with a much lower surface temperature of around 2,500-3,000 K. Thus, if by "cooler" you mean temperature, Mira is cooler, but Rigel's brightness and mass make it fascinating as well.