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