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