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