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