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