What does "If you are playing the Yankees, you don’t want the umpires to show up wearing pinstripes" mean? [closed]

Solution 1:

It's an illustration of the rule expressed in the preceding sentence. If you want to be (or appear) impartial, do not wear the uniform of one of the teams.

The [Yankees] home uniform is white with distinctive pinstripes and a navy interlocking "NY" at the chest.
Wikipedia

Solution 2:

In American Major League Baseball, the New York Yankees traditionally wear pinstripes on their uniforms.

https://ftw.usatoday.com/2013/04/yankees-pinstripes-origin-babe-ruth 1

Thus, for the umpires, who are supposed to be impartial judges, to "show up wearing pinstripes," would suggest they were, in fact, favoring the Yankees.