One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,5)(4,6)(7,8)(9,10)(11,17)(12,15)(13,16)(14,19)(18,23)(20,22)(21,24)(25,26)(27,36)(28,30)(29,38)(31,35)(32,34)(33,37)(39,40) involution — undirected(1,3,4,7)(2,5,6,8)(9,11)(10,14)(12,18)(13,19)(15,21)(16,17)(20,24)(22,23)(25,27)(26,33)(28,29)(30,34)(31,37)(32,39)(35,36)(38,40)(2,6)(5,8)(9,12,13,20)(10,15,16,22)(11,18,19,24)(14,21,17,23)(25,28,29,27,31,39,32,37)(26,30,38,36,35,40,34,33)(10,16)(14,17)(15,22)(21,23)(25,29,31,32)(26,34,35,38)(27,28,37,39)(30,36,40,33)(11,19)(14,17)(18,24)(21,23)(25,30,29,36,31,40,32,33)(26,28,38,27,35,39,34,37)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.