Last week I noticed a camouflage Swamp Thing action figure that differed from the one in my collection. After doing some investigating on the internet I found that there are two Camouflage ST figure styles. The difference in the figures is the painted green pattern on the figures chest.
The more readily available figure has a full green chest.

The variant that doesn’t seem as common:

I should have noticed the difference on the back of the figure cards.

The more intricately painted camo version is used in ads but they seem harder to find for purchase. I can’t prove any of this since I have not been able to find any info on the internet BUT if I was to use a little misguided logic I would say that the intricately painted camo versions were the first production run. This would explain why they were used in advertisements. The figure had a second run with a more simple paint job to cut down on production time/costs. This second run had a larger production number which is why it is easier to obtain today …sounds ok I suppose.