When Spider-Smith falls in the plasma ring, he gets ripped apart and you can see red blood flying around. His blood should be blue, shown when Spider-Smith strokes Human-Smith's scratch and it oozes blue blood.
I don't think Spider-Smith caused that spider scratch to bleed. I think that the blue that was visible was muscle tissue which was forming. And besides, blood is red because of oxygen mixing in with it. Unless this planet has no oxygen (which would be bad for the Robinson's) the blood would turn red immediately. But, it's not blood, so it doesn't matter. :-D
Undrhil