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