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