User blog comment:BunsenH/Titans vs. Colossals/@comment-31797469-20191215194520/@comment-31797469-20191215202429

From my understanding, All three current Island Skins are atop Titans (Harvherd, Sweti and Hahoo) as is both Magical Islands (Cruv’Laapht and Faesodd).

All other Islands (Natural, Mirror, Fire, Shugabush, Ethereal, Tribal, Gold) are on top of Colossi.