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