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