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