You saw a pigeon with a blue id tag?

I don't know where the blue tag is from, but I have been watching a pigeon with a blue tag in our parking lot for at least a month now. I wish I knew where he's from???

I have a pigeon that roosts on my balcony every night with a blue tag on it's leg, no what info is on it as can't get close enough to the pigeon but I'm in Gravesend.