Uniform Regulations: Acceptable Undergarments & Sliding Equipment

Question
Hi,
Does it matter if a player is wearing black spandex or sliding cuff even though
their uniform colors are white and blue?

Answer
No

Exposed undergarments are considered part of the uniform.  They must be black, white, gray, or school colors.

A sliding pad is equipment not part of the uniform.  There are some rules to regulate equipment that leave a lot to the umpires judgement.