In 1877 and 1878, we have newspaper descriptions and a photo from the newspaper that explain and show the team wore plain white pullover shirts. Closer inspection it appears the team may have had a thin brown band on their caps, and a brown piping around the neck of the shirt.
Newspaper Accounts
St. Louis Globe Democrat: April 1, 1877
The St. Louis Club will not wear tight fitting shirts this summer. Last year they got too big for their clothes, and what they want this year is plenty of room to swell out.
Team Colors
Brown – PMS 732
Off-White Fabric – CMYK: 1/2/3/0
Cardinals Uniforms & Logos 