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