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)(15,22)(20,23)(21,24)(25,26)(27,38)(28,34)(29,40)(30,37)(31,36)(32,35)(33,39) involution — undirected(2,5)(3,7)(9,11,14,22)(10,15,17,19)(12,20,18,24)(13,23,16,21)(25,27)(26,33)(28,32)(29,30)(31,39)(34,37)(35,40)(36,38)(1,2)(3,6)(4,5)(7,8)(9,12,14,18)(10,16,17,13)(11,20,22,24)(15,21,19,23)(25,28)(26,33)(27,32)(29,31)(30,39)(34,35)(36,38)(37,40)(2,5)(6,8)(10,17)(12,18)(15,19)(20,24)(25,29,31,28)(26,34,36,40)(27,30,39,32)(33,37,38,35)(1,3,4,7)(2,6,5,8)(9,13,14,16)(10,18,17,12)(11,21,22,23)(15,20,19,24)(25,30,31,32)(26,35,36,37)(27,28,39,29)(33,34,38,40)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.