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