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