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