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