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