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