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