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