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