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