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