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