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