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