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