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