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