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