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