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