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