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