Ummm.... this isn't true. Iguanas have red blood.

There is a genus of skinks that have green blood. But they are the only lizards I know of that don't bleed red. And technically there blood is red, but has so much biliverdin in it (a byproduct of hemoglobin break down) that it looks green.

Iguanas have been hunted and eaten for hundreds if not thousands of years. They bleed red. You can Google and find pictures of ones with scrapes on their sides, and they are bleeding red. Who told you they bled whatever color they were?