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