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