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