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