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