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