The staining isn't blood - it's classic foxing - discolourations from any number of things - including old cleaning products, sweat, and mould. Because its white cotton you should be able to remove the staining with cleaning. Washing in soap and water will help, but I think its been there for a while, so you will probably have to use something like oxyclean to really get the staining out.You may want to remove the patch with the red stitching first because it may take out all the red colouration, or cause it to bleed. Also, if you use oxyclean you should remove the shell buttons first, otherwise they will get damaged and end up with a rough surface.