Here's another useful thing to be aware of for those who want to create transition areas from regular to lava caverns: the lava caverns pieces are painted with the stone around the lower, lava-filled areas dark and scorched, but the upper parts of the walls (where the stalactites are) looking more like normal caverns. It's as if Hell is bubbling up from below. So, one could easily create a multi-level build with Caverns at one level and then lava caverns one level lower down, with a cliff edge/ledge/etc. at the downward transition, and the color scheme would flow very naturally.