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