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