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