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