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