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