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