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