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)(11,15)(12,16)(13,14)(17,23)(18,21)(19,24)(20,22)(26,32)(27,28)(33,39)(35,36)(1,3,5,8)(2,6,4,7)(25,26,31,32)(27,34,28,29)(30,33,38,39)(35,40,36,37)(10,14)(15,21)(16,22)(23,24)(25,27,31,28)(26,29,32,34)(30,36,38,35)(33,40,39,37)(9,11,13,18)(10,15,14,21)(12,19,20,17)(16,24,22,23)(25,28,31,27)(26,29,32,34)(30,35,38,36)(33,40,39,37)(1,4,5,2)(3,7,8,6)(9,12,13,20)(10,16,14,22)(11,17,18,19)(15,23,21,24)(25,29)(26,27)(28,32)(30,37)(31,34)(33,35)(36,39)(38,40)(9,10)(11,15)(12,16)(13,14)(17,23)(18,21)(19,24)(20,22)(25,30,31,38)(26,33,32,39)(27,35,28,36)(29,37,34,40)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.