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