Morandi vs. Van Gogh: Color

Below you see two paintings by Giorgio Morandi and two paintings by Vincent Van Gogh.

Describe the differences between the artists' choices of color palette and subject matter in these particular paintings.

Also, how does the choice of color palette influence or affect the subject matter?

Still Life, 1955, Giorgio Morandi

Still Life, 1955, Giorgio Morandi

Irises, 1890, Vincent Van Gogh

Sunflowers, 1888, Vincent Van Gogh