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