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