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)(11,21)(12,26)(13,20)(14,18)(15,19)(16,23)(17,28)(22,30)(24,32)(25,31)(27,34)(29,35)(33,37)(36,39)(38,40) involution — undirected(2,5)(6,8)(9,11,14,24,15,25,13,23)(10,16,20,31,19,32,18,21)(12,22,29,39,27,37,28,38)(17,33,34,36,35,30,26,40)(1,3,4,7)(2,6,5,8)(9,12,13,28,15,27,14,29)(10,17,18,26,19,35,20,34)(11,22,23,38,25,37,24,39)(16,30,21,36,32,33,31,40)(10,18,19,20)(12,27)(16,21,32,31)(17,34,35,26)(22,37)(28,29)(30,40,33,36)(38,39)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.