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