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