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