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