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