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