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