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