My wife likes the Shale Gray also - actually, we are probably looking at Accents and she likes Triathlon Gray, but same idea.
Basically, she likes light cars and I like medium cars. (And I tend to like blue).
On the AD Elantras (Shale Gray would be about my third or fourth choice - probably hers also):
1 - Lakeside Blue - Really like this color.
2 - Electric Blue - Need her opinion. I like it, but she might think it is too trendy.
3 - Scarlet Red - Haven't seen in person, but I like red cars. Wife says it attracts police and only looks good on sports cars.
4 - Shale Gray - Wife thinks it looks professional and would probably put this third. TBH - I rarely wash/wax cars and gray tends to look okay when it is dirty, so it's high on my list b/c of that.
5 - Symphony Silver - I've never had a silver car - tend to like, wife is fairly neutral on this.
6 - Quartz White Pearl - Doesn't really count. Wife's car is this color now. She likes it. We won't have his and hers same color car. I previously inherited a plain white car of hers and hated it. If it ever gets dirty you have to wash the entire car.
7 - Phantom Black - See Item 6 - even worse than white to keep clean.
8 - Mineral Beige - This is likely the most practical color in terms of not showing dirt. It would be my wife's first choice after Quartz White, second choice overall. Just doesn't do anything for me - looks boring ...