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