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