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