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