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