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