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