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