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