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