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