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