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)(11,19)(12,15)(13,17)(14,23)(16,21)(18,22)(20,24)(25,26)(27,31)(28,33)(29,32)(30,34)(35,38)(36,40)(37,39) involution — undirected(2,5)(6,7)(9,11,13,12)(10,15,17,19)(14,20,22,21)(16,18,24,23)(25,27,30,37)(26,31,34,39)(28,36,29,35)(32,38,33,40)(9,12,13,11)(10,16,17,24)(14,20,22,21)(15,18,19,23)(26,32)(27,35)(28,29)(33,34)(36,37)(38,40)(1,3,4,8)(2,6,5,7)(10,17)(11,12)(18,23)(20,21)(25,28,30,29)(26,33,34,32)(27,35,37,36)(31,38,39,40)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.