The galaxy that contains mostly older stars with a red color is called an elliptical galaxy.

Here's why:

* Older Stars: Elliptical galaxies have formed very early in the universe's history. They have had billions of years to burn through their hydrogen fuel, leading to the formation of older, cooler stars.

* Red Color: Cooler stars emit light primarily in the red part of the spectrum. Therefore, elliptical galaxies, populated by these older, cooler stars, appear redder than other types of galaxies.

* Lack of Gas and Dust: Elliptical galaxies typically have very little gas and dust. This means there is little material for the formation of new stars, explaining why they predominantly contain older stars.

Let me know if you'd like to learn more about elliptical galaxies!