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