http://www.i-mef.usmc.mil/msc/1fssg/KVN/Deployed/redpatchlore.html
Red Patchers are logistics Marines, specifically a landing support Marine (I was a Logistics Officer a long time ago). We wore red patches on our pants and one on our cover.
From the link above:
Support Marines Wear Red Patches of Honor
October 1, 2004
By Lance Cpl. Martin R. Harris
This illustration is displayed on the 3rd Transportation Support Battalion's farewell certificate for departing Marines. (Illustration by Lance Cpl. Kylene A. Kasch)
CAMP FOSTER , OKINAWA , Japan - You see them everywhere on Marine Corps installations -- Marines with small, red patches uniformly stitched to their camouflage trousers and covers. But what many may not know is that these Marines, with their distinctive, red patches, are symbolic of a uniform change that dates back to the bloody beaches of World War II.
Support Marines first adopted the red patch because of confusion between infantry Marines and landing support Marines during the World War II island-hopping campaign. Commanders were having trouble distinguishing between combat and support Marines, often leading commanders to send landing support Marines into front-line action.
When a lieutenant from the infantry ran up to a support Marine and said, "Grab your rifle, you're coming with me," the Marine had no way to prove that he was a support Marine. The support Marine grabbed his rifle and went, which led to serious breakdowns in the flow of supplies and gear, explained 1st Sgt. Stephen A. Bell, Headquarters and Service Company, 3rd Transportation Support Battalion, 3rd Force Service Support Group.
This problem was addressed at a 2nd Marine Division planners' conference, which was held after the battle of Tarawa in 1943. The division planners decided to have a red patch sewn on the support Marines' covers, or hats, and trousers, setting them apart from infantry Marines, according to retired Marine Col. James A. Donovan, former editor of "Leatherneck Magazine."
The new patch not only helped the landing specialists, but it also worked in reverse order, preventing "gung ho" support Marines' from moving into combat areas, Bell explained.
Wow! That's fascinating! Thanks for posting it.
My son was support in Iraq, but the enemy there doesn't seem to care. Then again, a red patch probably wouldn't have kept the Japanese from killing a Marine in WWII either. There just aren't many 'front lines' in Iraq.....