Pros:

 - Spitter spits blood.
 - Comes out red mixed with green (in my case).
 - Something different than the bright green.

Cons:

 - In my case it's not just red, but mixed with the original green.
 - Slightly(!) pink in dark areas.

Conclusion:

I was looking for a different color for hte Spitter's goo, preferably a darker green or actually more yellow-green, instead of the original strong cartoony bright green. But for me this mod actually turns it into a mix of the original green and red. It seems as if the red layer is on top of the original green, so the original seems to stay for some reason. It's actually kind of a cool mix. I must say, as pointed out, it does come across slightly pink in darker areas, but that's just the lighting. At least it something different. One drawback is that it seems to work differently for different people.
All in all, it's a nice mod to bring something new to the game.