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