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