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