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