One vertex per element, one color per generator, with an edge from x to x·s.
(9,10)(11,17)(12,19)(13,16)(14,15)(18,24)(20,21)(22,23)(26,32)(28,34)(33,38)(35,37) involution — undirected(1,2,4,6)(3,5,8,7)(9,11)(10,12)(13,18)(14,19)(15,17)(16,20)(21,22)(23,24)(25,26,31,32)(27,33,29,38)(28,30,34,40)(35,36,37,39)(1,2)(3,5)(4,6)(7,8)(10,15)(12,17)(16,23)(20,24)(25,27,31,29)(26,33,32,38)(28,35,34,37)(30,36,40,39)(9,12)(10,11)(13,20)(14,17)(15,19)(16,18)(21,23)(22,24)(25,28,31,34)(26,30,32,40)(27,35,29,37)(33,36,38,39)(1,2)(3,7)(4,6)(5,8)(9,13,14,22)(10,16,15,23)(11,18,19,21)(12,20,17,24)(25,29,31,27)(26,33,32,38)(28,37,34,35)(30,36,40,39)(1,3)(2,5)(4,8)(6,7)(9,11)(10,12)(13,21)(14,19)(15,17)(16,24)(18,22)(20,23)(25,30)(26,34)(27,36)(28,32)(29,39)(31,40)(33,37)(35,38) involution — undirectedA 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.