How the hell did Dutch's team miss the blood?

[bendinglight]

They were looking for human blood.

This. At the end of the day, that's not something they would be looking for. Depending on how tunnel visioned they were looking for human blood, probably just went right past their notice.

Agreed. Also, at this point the team had lost two members which is probably something they have not experienced before or if they have, it would be incredibly nerve-wracking to have your friend/team member killed without knowing what/who it is. That could shake someone to the core and have them overlook something like the glowing green blood.

[razeak]

I took my son squirrel hunting. I kept trying to show him the 3 or 4 squirrels I could see. They were moving and standing out quite obviously due to the movement. He couldn't locate them to save his life because he was looking for the image of a squirrel, not movement.  In a adrenaline filled moment, this isn't even surprising, even if it is bright green .

[bendinglight]

Not to mention.....since Thermal vision makes non heat based objects blend in together, how does even the Predator notice the traps laid around the camp?

The script has a mention around traps/trip wires in particular showing up in the Predator's vision (or referenced as the 'Observer' in the script).

36     EXT. JUNGLE - OVERHEAD - ALTERED P.O.V. - DAY         36

         SEEN THROUGH HEAT-SEEKING VISION, FOCUSED ON Blain
         and Mac, lying in the grass below, their bodies
         outlined in LUMONOUS AUREOLES.  The Observer SEES the
         NETWORK of TRIP WIRES guarding the approaches to the
         machine gun nests.  The wires GLOW as if ELECTRIFIED,
         standing out in hard-edged relief in contrast to
         the jungle foliage.  He moves higher into the forest
         canopy.

[Yautja888]

The green blood was clearly less obvious in vhs

More seriously, they were looking for human related clues at this point, so some green blood splattered
on green leaves, is not that obvious, besides the predator was wounded by Mac's first weapon, so the
blood was near the spot where they were all firing.They went far away from that spot to look for clues

[City Hunter Yautja]

The real answer, they thought one ofgreen colored  glowsticks broke in the gun fire and leaked all over the leaves. An honest mistake.