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