I don't know about other species of butterflies, but Monarchs only feed and reproduce on Milkweed species which contain cardiac glycosides (toxins). This gives them a degree of protection, along with the warning coloration of both the caterpillar and the adult. The chrysalis is green as in the picture, and is quite well camouflaged on the plant as it matures. It only turns clear at the inception of the emergence of the adult butterfly, where the warning orange/black coloration shows through, so is protected at that point.
My chrysalis is now 8 days old (it emerges at 8 - 15 depending on conditions), and is still pale green and one would not notice it if unaware of its location. I also just found 4 more 1st instar caterpillars on the plants I had to buy quickly after the first caterpillar ate every single leaf of the first plant and was still not a chrysalis yet.
Anyway, there are many mimics of Monarchs in the bfly world that enjoy some degree of protection from that.