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