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