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)(11,15,18,16)(12,17,20,21)(19,22,24,23)(25,26,31,30)(27,34,29,32)(28,33,36,38)(35,40,37,39)(3,7)(5,8)(9,11)(10,15)(12,19)(13,16)(14,18)(17,22)(20,24)(21,23)(25,27,31,29)(26,32,30,34)(28,35,36,37)(33,39,38,40)(1,2)(3,5)(4,6)(7,8)(11,18)(15,16)(19,24)(22,23)(28,36)(33,38)(35,37)(39,40) involution — undirected(1,3)(2,5)(4,7)(6,8)(9,11)(10,16)(12,19)(13,15)(14,18)(17,23)(20,24)(21,22)(25,28)(26,33)(27,35)(29,37)(30,38)(31,36)(32,39)(34,40) involution — undirected(1,2)(3,5)(4,6)(7,8)(9,12)(10,17)(11,19)(13,21)(14,20)(15,22)(16,23)(18,24)(25,29,31,27)(26,32,30,34)(28,37,36,35)(33,39,38,40)(9,13,14,10)(11,16,18,15)(12,17,20,21)(19,22,24,23)(25,30,31,26)(27,34,29,32)(28,33,36,38)(35,39,37,40)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.