The more logical answer to what hair color kvthm kids would have is whether Grey hair is recessive. Like does it technically fall under blonde or should we treat it as lighter shade of black? (black is dominant while blonde is recessive but that's not taking into account what Alhaitham's mom's hair was so we can't do a hypothetical punnet square) So its really up in the air. Aesthetic wise tho imo tho it's cute if they get their blonde hair from Kaveh while their heterochromatic green eye color from Haitham (just realized they'd borderline look like HI3 Otto spawn but Grey hair and reddish brown eyes aren't as appealing to imagine)

Kaveh is someone who's always neat and polished in canon but I feel Alhaitham finds him the most attractive when he's not all made up, the type where Alhaitham just can't keep his hands to himself when Kaveh looks like a divorced dad living alone and subsisting on instant ramen. Haitham who's like an affectionate cat and can't stop kissing and nuzzling against Kaveh's beard and inhaling his natural strong scent.

Kaveh pulling consecutive all nighters cause his latest client has been super unreasonable causing him to look tired asf. Kaveh with a five o clock shadow, eyebags, (this is weird but bare with me) and looks like he hasn't showered for some days. Kaveh though naturally beautiful has the weird charm where he looks alluring when he's scruffy looking.

Anyways thanks for letting me ramble hope you have a good day 🙋🏽‍♀️💖🔥