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