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