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