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