Nowadays mojo bags are often color coded: yellow for court case, red for love, purple for success or mastery, green for money. Red was the most traditional color, though, because it is powerful and because red flannel was commonly available, back in the day. I prefer red for all purposes, but I may rethink this.
Like many conjures, I put charms & symbols on mojo bags to tell them apart. I have metal dollar signs, crowns, hearts, and little blue "evil eye" beads. But today I was putting together two protective mojos: one "Leave Me Alone or Die" and one "Protect My Car." And no skulls or cars in my charm collection. No embroidery thread either.
But my daughter is an artist, so...

I just asked her to draw the skull for this "Leave Me Alone or Die" mojo bag.

Naturally, this Protect My Car mojo was even easier. (It'll get an Evil Eye bead, too, as soon as the last remaining ingredient arrives.)

And here's a honey jar for someone else who needs the Housing Authority to treat them right.