Talking about blood stains (not the blood splash!), you can remove ALL blood stains by only editing one file which is SplatData.slk. You can find it in the warcraft 3 MPQs (I took the one in war3x.mpq).
However, it takes some understanding about event objects, modeling for you to be able to understand it easily.
Maps below is the example effects that can be achieved by editing SplatsData.slk, try to use the paladin provided to kill the footmen:
Blue Blood Stain.w3x - Upon death, the footman leaves a blue colored blood stain rather than the red one
No Blood Stain.w3x - Upon death, the footman does not leave any blood stain