if troll lips are naturally black, why do the guys not get drawn with black lips? Im not trying to disagree with the cannon, i am illegitimately confused

It’s canon for all trolls, but it really depends on how the panel is drawn.  Females are almost always drawn exclusively with black lips unless they are wearing lipstick of a different color.  Males, however…

Actually, they usually have black lips too.  It probably isn’t as noticeable (especially for sprites) since the girls are drawn with somewhat feminine lips while the boys have teeth like something out of a dentist’s nightmare.  Ultimately, it depends on the style of the panel.