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