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)(11,17)(12,20)(13,14)(15,19)(16,21)(18,22)(23,24)(25,26,30,31)(27,28,32,36)(29,37,38,33)(34,40,39,35)(1,3,5,8)(2,6,4,7)(26,31)(27,32)(33,37)(34,39)(10,14)(15,17)(16,20)(22,23)(25,27)(26,28)(29,34)(30,32)(31,36)(33,35)(37,40)(38,39) involution — undirected(9,11,13,19)(10,15,14,17)(12,18,21,24)(16,22,20,23)(9,10)(11,15)(12,16)(13,14)(17,19)(18,22)(20,21)(23,24)(25,28)(26,32)(27,31)(29,35)(30,36)(33,39)(34,37)(38,40) involution — undirected(1,4,5,2)(3,7,8,6)(9,12)(10,16)(11,18)(13,21)(14,20)(15,22)(17,23)(19,24)(25,29,30,38)(26,33,31,37)(27,34,32,39)(28,35,36,40)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.