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