Pre-Pupal Luna Moth Caterpillar

Caterpillars
Location: Clarks Summit,Pennsylvania
August 3, 2011 11:00 am
one of my friends found this at their house.I think it’s a luna moth caterpillar,but they are green not red.
Signature: Joey M

Hi Joey,
You are correct that this is a Luna Moth Caterpillar.  Many caterpillars change color, often darkening, just prior to pupation.  This is a pre-pupal Luna Moth Caterpillar.