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)(11,18)(12,14)(13,15)(16,22)(17,21)(19,24)(20,23)(25,26)(27,35)(28,33)(29,31)(30,34)(32,37)(36,39)(38,40)(1,2)(3,5)(4,6)(7,8)(10,14)(11,19)(15,17)(20,22)(26,31)(27,36)(28,30)(32,39)(35,40)(37,38) involution — undirected(1,3,4,7)(2,5,6,8)(10,15)(13,21)(14,17)(16,24)(18,23)(20,22)(25,27,29,37)(26,32,31,35)(28,36,30,38)(33,40,34,39)(2,6)(5,8)(9,11,12,19)(10,16,14,23)(13,22,21,20)(15,24,17,18)(25,28,29,30)(26,33,31,34)(27,36,37,38)(32,40,35,39)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.