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