I have some headcanons about troll/human hybrids. Normally their skin is a more desaturated shade of their human parent. Their horns are shorter than full blooded trolls and start to grow in once they’re around 4. Their blood is a combination of the troll parents blood + red from the human parent. This results in the majority of hybrids having blood like purple, violet, magenta, red, brown and orange. It’s uncommon for them to have green and very near impossible for them to have blue as indigo blooded troll and human would result in violet usually but sometimes purple or fuscha.

Rose and Kanaya were able to get a child with a more saturated skin tone and longer horns as well as green blood due to a combination of rose being able to stack the odds for a more favourable outcome and kanayas experience tending to the mother grub