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