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