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