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