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