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