Ansel Adams was one of the most prolific and well-known photographers of the 20th century. He is most famous for his black and white landscape photographs of the American West, particularly Yosemite National Park. However, he also used color filters when shooting in black and white.
Adams typically used red or orange filters when photographing landscapes. These filters would darken skies and make clouds stand out more. They would also increase contrast between different objects in a scene. Red filters were especially useful for bringing out detail in shadows.
Orange filters had a similar effect to red ones, but were not as strong. They could be used to subtly enhance a photograph without making too much of an impact.
Yellow and green filters were less commonly used by Adams. Yellow filters would lighten up dark areas in a scene, while green ones would darken skies even further (useful for stormy weather). Blue and violet filters were almost never used, as they tended to wash out colors too much.