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