One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,7)(4,6)(5,8)(9,10)(11,18)(12,16)(13,15)(14,19)(17,21)(20,23)(22,24)(25,26)(27,35)(28,34)(29,31)(30,33)(32,38)(36,39)(37,40) involution — undirected(1,3,4,8)(2,5,6,7)(9,11)(10,14)(12,19)(13,20)(15,22)(16,18)(17,23)(21,24)(26,31)(28,30)(35,40)(36,38)(10,15)(13,21)(14,22)(16,17)(18,23)(20,24)(25,27,29,37)(26,32,31,39)(28,38,30,36)(33,35,34,40)(2,6)(5,7)(10,16)(11,19)(15,17)(20,24)(25,28,29,30)(26,33,31,34)(27,36,37,38)(32,40,39,35)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.