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