Most Helpful Girl
OPI has a color called Bastille My Heart that I think is dark maroon.
My suggestion is to go to OPI's website. Click "Nail Colors" at the top, then pick "All OPI Colors" from the drop down menu. Scroll through the little swatches until you find one that's dark maroon to you. Write down the name and go to the nearest salon/beauty supply store and buy that color.
OPI is the best nail polish brand by far.