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