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