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