In Lionni's fourth mouse fable his familiar little gray rodent is set against still a fourth distinctive background -- this one not collage but double-page textured paintings in orange-browns and blues, subdued to match the "quietest corner of the Willshire woods" where % community of field mice lived a peaceful life." When the country mice hear about Fat Tuesday and set about preparing their own Mardi Gras, brightly colored ribbons are seen dangling from the trees. The mice make ferocious masks and one even paints her tail green, but growling about in the masks gradually changes them until "the once peaceful community became a place full of hate and suspicion" (here a double page of scary big-jawed masks in wooded darkness). It takes a lone, unadorned mouse to bring the rest to their senses, whereupon they bum the masks in a fire that warms the dark pages, and -- except for that one green tail -- "everything was the way it had been before." Even though Frederick the poet remains the Lionni mouse with the sharpest message and most appealing personality, The Greentail Mouse has a simple, satisfying plot, some nicely modulated mood changes, and pictures that 'reflect and serve the story more organically than some of Lionni's more spectacular collages.