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