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