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