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)(11,15)(12,16)(13,14)(17,22)(18,21)(19,20)(23,24)(25,26)(27,32)(28,30)(29,35)(31,33)(34,36)(37,40)(38,39) involution — undirected(2,6)(3,7)(10,14)(15,21)(16,19)(22,23)(25,27)(26,32)(28,38)(29,36)(30,39)(31,37)(33,40)(34,35) involution — undirected(1,3,5,7)(2,4,6,8)(26,33)(27,37)(28,36)(35,39)(1,4)(2,7)(3,6)(5,8)(9,11,13,18)(10,15,14,21)(12,17,20,24)(16,22,19,23)(25,28,31,36)(26,34,33,30)(27,38,37,29)(32,35,40,39)(9,10)(11,15)(12,19)(13,14)(16,20)(17,23)(18,21)(22,24)(25,29,31,38)(26,35,33,39)(27,36,37,28)(30,32,34,40)(9,12)(10,16)(11,17)(13,20)(14,19)(15,22)(18,24)(21,23)(25,30,31,34)(26,36,33,28)(27,39,37,35)(29,40,38,32)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.