But before you can get your red tags, you need to phone Animal health (or whoever gives out herd/flock numbers In England - I am in Scotland) and get your won flock number.
Whoever sold the goats to you should have told you about registration etc - if you can get back to the seller you may be able to find out your boy's number. However that may be a lot of hassle, easier just to get a red replacement tag. As he is non-breeding it should all be quite easy.