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