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