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