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