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