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