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