About 500 enthusiasts assembled at Compton Avenue Park, to witness the novel encounter between the colored Blue Stockings and their white rivals. The game was hotly contested throughout, and was a tie from the third to the ninth inning...-The St. Louis Globe-Democrat, June 5, 1876
The implication was that the game between the Olives and Blues took place the previous day. The Blues scored first, getting a run in the second inning, with the Olives striking right back with a run of their own in the top of the third. Both teams scored two runs in the seventh and the game was tied 3-3 going into the ninth. In the top of the ninth, the Olives plated four runs to take a 7-3 lead. In the bottom of the inning, the Blues managed just a single run and lost 7-4.
At the Red Stocking Park, the colored Blue Stockings got away with their white antagonists in style...-The St. Louis Globe-Democrat, July 10, 1876
The second game between the Blues and the Olives, which most likely took place on the 9th, was a rout. The Blues jumped out to a 9-1 lead and won the game 16-9.
It seems (from what I can understand) that interracial games in this era were common in some areas but not in others. Lawrence Hogan, in Shades of Glory, mentions a game played between a white and black club in Philadelphia in 1869 and another played in Baltimore in 1870 but indicates that these were exceptions to the rule. He states that, in the North, the "opportunity to play a white team would be a significant feather" in the cap of a black club. However, he goes on to write that in New Orleans interracial games were "frequently held, without the need for (the) extensive diplomacy" that was needed to arrange these games in the North.
Where St. Louis fell along this spectrum is unknown at present.