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