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