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