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