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