Red is for replacement tags, I think.
I've just had a fun time with mine. I use Ketchum, who were brilliant. I needed 5 slaughter tags for the five tup lambs plus 4 sets of the ewe lambs I'm keeping. That was easy. Then I decided to get tags for all the sheep that have lost theirs - my three original ewes who only had one and have lost them, my tup and a 2009 ewe who are both down to one each and the two 2010 gimmers that I bought in with their EID tags in and their management tags in a bag (I don't have an applicator for them).
I had to look back flock numbers, ear numbers, choose colours. Ma heid was nippin'. The information is now on their registration papers. Anyway, got them now but I'm not putting them in yet. I'll put them in individual bags with their names on and put them in when I have to - save all this again