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