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