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