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