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