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