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