from the psp rulebook
9.7.3. The color yellow is prohibited on any players equipment or clothing, except that a player's jersey, pants, gloves or shoes may have yellow, so long as no part of the yellow coloring is more than 0.25 cm from some other color, and no more than 10% of any 5cm by 5cm square on clothing or item is yellow.
18.104.22.168. For reference purposes, 'yellow' is any color similar to Pantone colors 101, 102, 107, 108, 109, 116, 3945, 3955, 3965, and 803, although any head judge may prohibit any equipment they believe interferes with the judges' ability to officiate effectively.
5. Uniform 5.01 Protected Color. Players’ uniforms may not contain the color yellow, which is reserved as the “Protected Color” for paint.
10.01 Protected Color. Players’ equipment (including uniforms as provided in Section 5) may not contain yellow, which is reserved as “Protected Color” for paint. Loaders may not contain the color “Yellow”.