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)(11,14)(12,16)(13,15)(17,18,21,22)(19,20,23,24)(25,26)(27,30)(28,33)(29,34)(31,36)(32,37)(35,39)(38,40)(3,8)(6,7)(9,11)(10,14)(12,15)(13,16)(17,18,21,22)(19,20,23,24)(26,27)(29,37)(31,33)(35,38)(2,5)(6,7)(10,15)(11,16)(18,22)(19,23)(25,27,30,26)(28,31,36,33)(29,32,37,34)(35,40,38,39)(1,2)(3,6)(4,5)(7,8)(9,11)(10,12)(13,16)(14,15)(17,19)(18,20)(21,23)(22,24)(25,28,30,36)(26,31,27,33)(29,38,37,35)(32,40,34,39)(1,3)(2,6)(4,8)(5,7)(9,12)(10,11)(13,14)(15,16)(17,20)(18,19)(21,24)(22,23)(25,29,30,37)(26,32,27,34)(28,35,36,38)(31,39,33,40)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.