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