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