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