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