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