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