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