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