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