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