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