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