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