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