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