Regardless of the color of the shard, if I had gotten anything worth remembering I would have. All I know, whatever I open, it is junk, unless I get a duplicate of a good one I already have.
Most everything the game gives in the freebies or prizes is junk Class B or below.
as far as what is junk, if one goes to the lists out there of champ rankings, or even to the in-game reviews, following the Classes of God, S, A, B, C, D:
I have some in the S class, A Class, but B or less is hit or miss, mostly what I call junk, good for holding temporarily to do upgrades but I am done wasting artifacts on them.
In the in-game reviews, if I see a bunch of ratings below 4.0 that is junk to me, although there are some one application use champs that one can hold like for CB or Fire Knight.
I have a Coldheart, several Apothecaries, M Mage, the four starter champs, but nothing really flashy and dazzling like I see in the arena.
After 3 years I have gotten 2 legendaries champs, one A class, one B class, nothing fancy.
Oh well, I like those videos on u-tube that talk about making the most out of your rares, but of course everything with them is 6* and Lvl 16, so I am not in their league. They also sit there with many millions in silver and gems, if you don't like your masteries just move them around, like so, lol...