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