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