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