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