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