From the book "Ghosts of Onyx", the Spartan III's SPI armor. The armor is basically more enahnced ODST armor, with a "chameleon" type of plating, that kind of makes it like a weaker version of the active camo that the Elites have. And more specifically, no energy shields.

But then, the Spartan III's were made to be more numerous, and easier to make, so they went for quantity over quality this time.

They even used a cut down version of the Battle Rifle.

I was surprised that I could not find a scanned image of the armor online at all... Even the Halo Wiki's never had anything, only the shot of the crouching SPI armor on the cover of the book.

Thankfully, I was just trying to find a more convienent picture of the armor... As I have "The Art of Halo 3" book, which has a shot of the front and back of the SPI armor. It was just kind of awkward using the book and drawing at the same time.

The helmet is similar to the EVA Helmet from Halo 3's multiplayer, but there are quite a few differences.