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)(25,26,30,33)(27,34,36,32)(28,31,39,29)(35,37,40,38)(1,2)(3,7)(4,6)(5,8)(9,11,15,21)(10,16,17,18)(12,19,22,24)(13,20,14,23)(25,27)(26,32)(28,35)(29,37)(30,36)(31,38)(33,34)(39,40)(1,3)(2,5)(4,8)(6,7)(9,12)(10,13)(11,19)(14,17)(15,22)(16,20)(18,23)(21,24)(25,28,31,33,30,39,29,26)(27,35,38,34,36,40,37,32)(3,8)(5,7)(9,13,15,14)(10,12,17,22)(11,20,21,23)(16,19,18,24)(26,33)(27,36)(28,39)(37,38)(2,6)(5,7)(9,14,15,13)(10,12,17,22)(11,20,21,23)(16,24,18,19)(25,29,30,31)(26,28,33,39)(27,37,36,38)(32,35,34,40)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.