I had another thread here about trapdoor loads, and the question came up about different methods of marking brass to indicate different loads.
I came up with nickle cases until I learned they were hard on dies. Then someone suggested Birchwood's Brass Black, but didn't know how well it would work.
I promised to try the idea on some junk brass and get back to everybody.
I had some junk .45/70 brass I cleaned, and polished. put the Brass Black on them, and the heads are now black.
I did learn that you need to clean any leftover residue from whatever you use to clean your brass, or the Brass Black just beads up on the surface. So now, I'll have a box of brass with black heads to indicate loads for my Trapdoor, and my Rolling block. Thanks, Mike

different collor fingernail polish around the primer to seal it maybe?

I use a sharpie on the base. I write down numbers or letters that  indicate the load. Example b1=3.5grains 148grn wadcutter in my note book.

I use sharpie bands around the case body.  That way I can ID them on the ground, in the mag, in my ammo bucket, etc.

1 blue band = once fired, loaded with H335, 2 bands = twice fired, etc.  I had to adopt this system because I was always getting my brass mixed up.

I use paint markers. regular markers don't work well, but the paint ones do. Yellow, red, green, white, black, etc. Helps keep track of load count, and/or lot.

I've had great luck with sharpies.

Sharpies work for me also.

When working up a load I usually load ten rounds each of five different powder charges.  I write the powder charge on the side of the case with a black sharpie.  The writing holds up very well and will not come off until I tumble the fired cases.

real hit and miss for me. Sharpies don't seem to work well if there is any oil or lube present. Sharpies also rub off pretty easy for me.

YMMV

Ah... I tumble after resizing to get the lube and such off.

I use a Sharpie across the primer.  Different colors are specific loads in that caliber and they never change.

Dykem