I have a litter of german shepherd puppies, at what age is it safe to put the colour collars on them, they are 10 days old and im a bit scared incase they harm themselves

What type of collar are they?
People I see using them do so from birth as the idea is to use them to be able to tell pups apart which you would need to do if your keeping an eye on weight gain/loss in them as they grow.

If your using the Velcro type I have seen a few people with pups who ended up with sore patches from rubbing of it while nursing. People advised to cut them thinner to avoid the issue.

I've had them on from day 5.

I have had them from day one but they are the thin velco type, suitable for newborns.

I bought some from the Internet, thin Velcro ones from birth (although I didn't end up using them as each pup had different marking/colouring so could identify them through written descriptions), but also came with larger thicker ones for when they're older and bigger

I don't like the idea of collars so stick to the old way of nail varnish, a dab on the ears or top of the head, you do have to renew it if it wears off but never seems to have had any problems except the pups being referred to as "left ear" or "red head"  and not having names

they have a  safety fast release clip on them, got them off ebay, can adjust size also