My new Sport II came with a few minor scratches on the front sight/gas block, and the forward assist button. Is there a way to touch it up that will not be more noticeable than the scratch.

Flat black enamel and an artist's brush will get the job done. Use a MINIMUM amount of paint for best results.

I might get shot for saying this, but with my rifle, I'll use a bluing pen and if that doesn't work after a few applications, then I'll use a sharpie real lightly and try to buff it up some with a rag to make it match a bit better. It's an AR, they aren't meant to be pretty, I just don't want mine flashy.

Black sharpie works better than you might think for small marks, but it's not very durable rubs off pretty quick if used anywhere that gets handled.

I use Birchwood Casey Flat Black Touch Up Pen: Birchwood Casey Super Black Touch Up Pen Flat

Yep. Me too. Noticed a small spot up front by the gas block/front sight that had a small scratch. Must have somebody new on the Sport II assembly line. Was going to touch it up but just haven't taken the time to grab one of the Birchwood Casey touch up pens. They work good for the small stuff like that. I've used them before on a Rem. 870 Express. (waterfowl gun, gets a few new scratches every season it seems like)

For small stuff, I've used flat black primer spray paint. Not spraying the metal of course but spray a bit inside a shopping bag, and dab the bare area with a toothpick. Spray paint is thin enough where it doesn't bulge and when it dries it's more or less level.

Clean the area with rubbing alcohol first. Carefully apply a small amount of paint with a sharp toothpick, let it dry and see if you need another coat. If it bleeds or doesn't look right, wipe off with the alcohol and start over.