2 big reds, I've only personally seen blue hoof horn when someone has soaked in, or ODed their horse on copper!
Re supposed different tensile strength of dark & light hooves, the proof should be in appies & others with striped horn - if white was inherently weaker, they wouldn't have survived the rat race, because their hooves would naturally crack at the 'fault lines'.
OP, I think that fallacy came about because light hooves show insult & injury clearly, whereas dark hooves can hide a lot.
OP, basically agree with Rialto. If your horse is getting well balanced nutrition generally, then as hooves/hair/skin is part of the body, it should also be getting what it needs. So if the Khonke's fills all appropriate gaps, that should be adequate. From my personal study(not a nutritionist) I think the Khonke's range does sound good. Just that my horses wouldn't touch their RB & they were contradictory & rude to me about it, so I don't deal with them...
BUT the subject of 'well balanced' is a bit of a minefield & many 'accepted facts'(such as Ca/Mg balance for eg) have been strongly disputed in recent times. Especially if you have hoof issues, you may want find gravelproofhoof.org enlightening.
Don't know about the sunflower seeds, or what levels are in whatever khnoke's you use, but lucerne is high in energy, potassium, calcium & protein, among others, which if in OD can all have a bearing on 'hyper' behaviour, among other things.
Oh & maybe a case of 'the Emperor's new clothes' but you will not see a difference in hooves due to nutritional changes in days or weeks. Changes to behaviour, body tension, etc, can happen very quickly though.