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