Hi , can you possibly post a photo ? There have been reports of chimera , where labs have two colours , but I don't know if these have been authenticated , what does your Vet have to say ?
Hi Mocky - have you checked with your vet? Always the first point of call for health information. Having said that, is it a darkening of fur? Or black patches of skin. Is he bothered by it i.e. itchy? Sometimes fungal infections can appear a little brown on the skin. My curiosity is piqued - a photo would be helpful. (though I still think the vet is your best option as none of us are qualified!)
That is reassuring Mocky - our dogs often have a mix of black brown and yellow genes. My black girl has very brown flanks when she is moulting/shedding hair.
Looks like his skin under his fur is black. Do you know what colour his parents were (though genetics of dogs is not my strong suit)
There is a webpage showing colour variations in purebred labs. Its quite interesting http://www.woodhavenlabs.com/mismarks.html
Hi yes Iv seen this, he’s not this bad hopefully, only other place is inside his ears like dirty marks x
@Mocky - From your avatar it looks like he has a shorter coat similar to my Teller and those black areas are just where you can see his skin, places devoid of undercoat. Sometimes patches on T's belly skin darken as you're describing. There is no itching, hair loss, or lesions and we think it's maybe a seasonal thing because the skin will lighten back up? In the summer T doesn't keep much of his undercoat on his sides and when he gets wet the skin shows through lending him what look almost like tiger stripes. Here's a picture of his belly in the summer, you can see the darker patches of skin near his armpits and legs.