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