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