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