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