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