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