No, it's not blood. Black and red isn't even my usual color scheme (for reference, that's dark green and light blue), I'm using it in reference to a larger project, should I ever finish it enough for me to post it. Instead, it's made from an image that's very well known in the community it comes from. I heavily changed the colors using the curves feature of paint.net and cropped a particularly interesting looking square of it to use here.

The first that manages to guess what the source image is correctly will be immortalized here.