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