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)(11,19)(12,16)(13,17)(14,18)(15,21)(20,24)(22,23)(25,26)(27,34)(28,38)(29,33)(30,32)(31,37)(35,40)(36,39)(9,11)(10,15)(12,20)(13,22)(14,21)(16,23)(17,24)(18,19)(25,27)(26,31)(28,36)(29,37)(30,35)(32,39)(33,34)(38,40) involution — undirected(1,3,4,8)(2,5,6,7)(9,12,14,13)(10,16,18,17)(11,20,21,22)(15,23,19,24)(27,35)(28,30)(31,39)(32,38)(34,40)(36,37)(9,12,14,13)(10,17,18,16)(11,20,21,22)(15,24,19,23)(25,28,29,30)(26,32,33,38)(27,36,37,35)(31,39,34,40)(9,13,14,12)(10,17,18,16)(11,20,21,22)(15,23,19,24)(27,35)(28,30)(31,39)(32,38)(34,40)(36,37)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.