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