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