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