I’ve been using gel pens as my grading pens for a long, long time. I used to buy variety packs, and then use pink, orange, and sometimes green. But lately, I’ve just been using pink.
Not too long ago, I saw pens being sold individually in the checkout line at Staples. I got a few. But this past weekend, I saw this:

I’ll have pink pens for ages! Nice!
What – no purple? That was usually my go-to grading color. Great contrast against white paper without the “here is where you screwed up” feeling.
How terrible is it that my first thought was, “Staples is still open?”
I approve of your (and Carol’s) color choice – it makes it harder for a kid to fake any marks.
Pilot G2 0.7mm are my favorite pens.