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