My horse is grey and he’s never been massively bothered by the flies or midges etv. My new Youngster is dark bay and they definitely bother him more.
I usually get away with a few squirts of fly spray for my grey on bad days and that’s about it!!
I've just sorted out a fly rug for Rose, she's dark bay (almost black) and covered in flies but so is the pony who is palomino. The late Bisto (tobiano) was plagued by them too. The little black thunder flies bite my scalp. Do I just have really aggressive flies?
My chestnut seems to attract them much more than my mostly white piebald, and my skewbald doesn't seem too bothered although he has tons of mane and forelock which keeps them off his face.
Greys generally don't attract flies. Didn't they do a scientific thing and that's why they developed that zebra stripe range? All fly rugs are pale coloured possibly as flies do not get attracted?
We get flies all year, but without a breeze the midges might be annoying around the muzzle.