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