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