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