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