It made Jim Crows law legal.
This is because it allowed segregation to continue, but said services had to be “equal” (though they really weren’t).
Here are why the other answers are wrong:
Jim Crow laws were removed in the 1950s and 1960s, and this case reinforced segregation.
This was not the first lawsuit heard by the court on race issues. One example of an earlier case is Dred Scott V Sandford.
Plessy was a person of color, and was not more white than black.