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