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