The unfirom is comprised of several components.
Page 485 - "The Book of American Pastimes" in the section "The National Game"
UNIFORM.--Caps: white trimmed with blue; blue star in middle of the crown. Shirts: white flannel, trimmed with blue; the letter "A" (German text) in blue, on the breast. Pants: blue cloth with white cord down outer seam. Belts: white and blue, with German-silver clasps in front, and the word "Athletic," in blue letters on white morocco, in the center of back.