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