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)(11,26)(12,31)(13,35)(14,37)(15,38)(16,24)(17,28)(18,25)(19,21)(20,34)(22,32)(23,27)(29,39)(30,36)(33,40) involution — undirected(2,5)(6,7)(9,11,15,29,17,30,14,21,18,12,32,34,16,35,27,33)(10,19,23,36,24,39,22,26,25,40,37,13,28,20,38,31)(9,12,14,33,16,30,15,34,18,11,27,21,17,35,32,29)(10,20,22,36,28,40,23,31,25,39,38,13,24,19,37,26)(1,3,4,8)(2,6,5,7)(9,13,15,20,17,31,14,19,18,36,32,39,16,26,27,40)(10,21,23,12,24,34,22,35,25,33,37,11,28,29,38,30)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.