Monster Rain wrote:I was thinking about priming them in red.
Does anyone know of a good primer to approximate this color?

No primer is doing the work for you here. This wasn't just primed and then washed a couple of times but worked up from black. If you want the same quality, I'd suggest black primer and then go the usual way from black to bright red. At least red is the easiest color to do
IMO.
But you could get the army painter primer (it's kinda like blood red, a bit deeper) and then wash it a few times. It won't look anywhere near this though.