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