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