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