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