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