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