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