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