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