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