On February 15 1896 — 1896 – The Louisville infield is being rebuilt with baselines of blue clay. In addition, blue semicircles will radiate out from first base and third base, joining at second base to form, along with the bottom half of the diamond, a heart.
Source:
Baseball Reference February 15
SABR Games Project
National Pastime February 15
Hall of Fame
Replay The Game
Retro Sheet