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