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