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