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