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