Predominantly red or predominantly blue singlets are allowed, as well as singlets mimicking the UWW color scheme. If a singlet is mimicking the UWW color scheme (there is not a single color that satisfies the rule for both red and blue), the following criteria must be met:

The dominant color of blue banded singlets shall be comprised of one of the following: black, blue, green, grey, purple or silver.

The dominant color of red banded singlets shall be comprised of one of the following: white, orange, pink, red, yellow, brown or gold.

Head gear is required for 14U, 12U, 10U, and 8U wrestlers.  Head gear is optional for 16U and Jr wrestlers.  

Singlet specific rules, illustrations, and examples of singlets that do comply and singlets that do not comply can be found here -  https://drive.google.com/file/d/17TwiuZMSNmBY821i3XcPzoexP3J6mdhp/view?usp=sharing