I've got a few pairs and aside from my 100 dernier pair I can't really tell the others apart unless I go to the bother of putting a leg in. Only a recent regular tights wearer too as usually wear trousers to work.
I bought tights from M&S today which had a little label in the back with type & dernier - genius! Why don't all tights manufacturers do this??
What do most people do to tell their tights apart? Or do you all just do the 'one leg in' test too? 
If you've found this page in search of tights that have been tried and tested by fellow Mumsnet users, you might find our guide to the best tights useful. Hope this helps! MNHQ