Cosboy is a xenogender similar to rosboy, where one is a boy but still feminine. However, in the case of cosboy, the gender is also xenic, relating heavily to space and softness. A cosboy is a boy whose gender is aligned with femininity and soft, space aesthetics. In that way, it is also partially an aesthetigender.
The black stripe in the flag represents space. The purple and grey represent softness. The blue represents being male and the pink represents femininity.