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