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)(18,20)(19,23)(25,26)(27,31)(28,32)(29,30)(33,38)(34,39)(35,37)(36,40)(11,15)(14,16)(18,20)(22,24)(26,30)(27,33)(32,35)(34,36) involution — undirected(9,10)(11,14)(12,13)(15,16)(17,18,21,20)(19,22,23,24)(25,26)(27,31)(28,35)(29,30)(32,37)(33,38)(34,40)(36,39)(1,2)(3,5)(4,6)(7,8)(9,10)(11,14)(12,13)(15,16)(17,19,21,23)(18,22,20,24)(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)(10,14)(12,15)(13,16)(17,20,21,18)(19,24,23,22)(25,28)(26,32)(27,34)(29,37)(30,35)(31,39)(33,36)(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.