I would like to know are pubic lice yellow.

Yes: They are yellow grey or rust in color.

Pubic Lice: The pubic louse (Phthirus pubis) is about 1 to 2 mm in length & when magnified looks like a crab. It is wingless, tan to grayish-white, flattened dorsoventrally, has 3 clawed sets of legs & a head which is significantly smaller than the rest of the body. Pubic lice look different than head or body lice. They don’t have the capacity to move on smooth surfaces. Adult lice die within 24 to 48 hours