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