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)(11,19)(12,13)(14,17)(15,18)(16,22)(20,23)(21,24)(25,26,31,37)(27,32,38,33)(28,34,39,40)(29,36,30,35)(2,5)(3,7)(9,11)(10,16)(12,20)(13,21)(14,23)(15,22)(17,24)(18,19)(25,27)(26,32)(28,30)(29,39)(31,38)(33,37)(34,35)(36,40) involution — undirected(1,3,4,7)(2,6,5,8)(9,12,15,17)(10,13,18,14)(11,20,22,24)(16,21,19,23)(25,28,31,39)(26,33,37,32)(27,29,38,30)(34,36,40,35)(2,5)(6,8)(9,13,15,14)(10,17,18,12)(11,21,22,23)(16,24,19,20)(25,28)(26,34)(27,29)(30,38)(31,39)(32,36)(33,35)(37,40)(9,14,15,13)(10,17,18,12)(11,21,22,23)(16,20,19,24)(25,29,31,30)(26,35,37,36)(27,28,38,39)(32,40,33,34)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.