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